> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://developers.hellosign.com/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://developers.hellosign.com/_mcp/server.

# Account Callbacks

POST 

This type of callback URL can be set up at the account level (either by setting it through an API request to "/v3/account" or on the Account Settings page on hellosign.com).
          
All signature request events that involve your account are reported to this URL. This includes events such as receiving a signature request, or when a signature request you've sent is signed by someone. Events are reported to the account callback URL for either requests originating on hellosign.com, or on a partner site, via an embedded flow.

You can set your account callback by using the [account API call](https://app.hellosign.com/api/account/post) or manually on the [settings page](https://app.hellosign.com/home/myAccount#api).

Reference: https://developers.hellosign.com/api/events/account-update-event-callback

## Request

### Payload

- `object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object or object`
  - Signature Request Viewed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_viewed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Signed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_signed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Signer Removed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_signer_removed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Downloadable Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_downloadable`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Sent Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_sent`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request All Signed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_all_signed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Invalid Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_invalid`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Email Bounce Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_email_bounce`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Remind Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_remind`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Incomplete QES Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_incomplete_qes`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Destroyed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_destroyed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Canceled Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_canceled`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Declined Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_declined`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Expired Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_expired`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Reassigned Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_reassigned`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Signature Request Prepared Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `signature_request_prepared`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Account Confirmed Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `account_confirmed`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `account` (object, optional)
      - `account_id` (string, optional) — The ID of the Account
      - `email_address` (string, optional) — The email address associated with the Account.
      - `is_locked` (boolean, optional) — Returns `true` if the user has been locked out of their account by a team admin.
      - `is_paid_hs` (boolean, optional) — Returns `true` if the user has a paid Dropbox Sign account.
      - `is_paid_hf` (boolean, optional) — Returns `true` if the user has a paid HelloFax account.
      - `quotas` (object, optional) — Details concerning remaining monthly quotas.
        - `api_signature_requests_left` (integer, optional, nullable) — API signature requests remaining.
        - `documents_left` (integer, optional, nullable) — Signature requests remaining.
        - `templates_total` (integer, optional, nullable) — Total API templates allowed.
        - `templates_left` (integer, optional, nullable) — API templates remaining.
        - `sms_verifications_left` (integer, optional, nullable) — SMS verifications remaining.
        - `num_fax_pages_left` (integer, optional, nullable) — Number of fax pages left
      - `callback_url` (string, optional, nullable) — The URL that Dropbox Sign events will `POST` to.
      - `role_code` (string, optional, nullable) — The membership role for the team.
      - `team_id` (string, optional, nullable) — The id of the team account belongs to.
      - `locale` (string, optional, nullable) — The locale used in this Account. Check out the list of [supported locales](/api/reference/constants/#supported-locales) to learn more about the possible values.
      - `usage` (object, optional) — Details concerning monthly usage
        - `fax_pages_sent` (integer, optional, nullable) — Number of fax pages sent
      - `settings` (object, optional) — Subset of configured settings
        - `signer_access_codes` (boolean, optional) — Returns `true` if _Custom access codes_ is enabled in Admin Console. [Read more](https://developers.hellosign.com/docs/sms-tools/walkthrough).
        - `sms_delivery` (boolean, optional) — Returns `true` if _Text message_ is enabled in Admin Console. [Read more](https://developers.hellosign.com/docs/sms-tools/walkthrough).
        - `sms_authentication` (boolean, optional) — Returns `true` if _Signer authentication_ is enabled in Admin Console. [Read more](https://developers.hellosign.com/docs/sms-tools/walkthrough).
  - Unknown Error Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `unknown_error`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - File Error Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `file_error`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Template Created Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `template_created`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `template` (object, optional) — Contains information about the templates you and your team have created.
      - `template_id` (string, optional) — The id of the Template.
      - `title` (string, optional) — The title of the Template. This will also be the default subject of the message sent to signers when using this Template to send a SignatureRequest. This can be overridden when sending the SignatureRequest.
      - `message` (string, optional) — The default message that will be sent to signers when using this Template to send a SignatureRequest. This can be overridden when sending the SignatureRequest.
      - `updated_at` (integer, optional) — Time the template was last updated.
      - `is_embedded` (boolean, optional, nullable) — `true` if this template was created using an embedded flow, `false` if it was created on our website. Will be `null` when you are not the creator of the Template.
      - `is_creator` (boolean, optional) — `true` if you are the owner of this template, `false` if it's been shared with you by a team member.
      - `can_edit` (boolean, optional) — Indicates whether edit rights have been granted to you by the owner (always `true` if that's you).
      - `is_locked` (boolean, optional) — Indicates whether the template is locked. If `true`, then the template was created outside your quota and can only be used in `test_mode`. If `false`, then the template is within your quota and can be used to create signature requests.
      - `metadata` (map from string to any, optional) — The metadata attached to the template.
      - `signer_roles` (list of object, optional) — An array of the designated signer roles that must be specified when sending a SignatureRequest using this Template.
        - `name` (string, optional) — The name of the Role.
        - `order` (integer, optional) — If signer order is assigned this is the 0-based index for this role.
      - `cc_roles` (list of object, optional) — An array of the designated CC roles that must be specified when sending a SignatureRequest using this Template.
        - `name` (string, optional) — The name of the Role.
      - `documents` (list of object, optional) — An array describing each document associated with this Template. Includes form field data for each document.
        - `name` (string, optional) — Name of the associated file.
        - `index` (integer, optional) — Document ordering, the lowest index is displayed first and the highest last (0-based indexing).
        - `field_groups` (list of object, optional) — An array of Form Field Group objects.
          - `name` (string, optional) — The name of the form field group.
          - `rule` (object, optional) — The rule used to validate checkboxes in the form field group. See [checkbox field grouping](/api/reference/constants/#checkbox-field-grouping).
            - `requirement` (string, optional) — Examples: `require_0-1` `require_1` `require_1-ormore` - Check out the list of [acceptable `requirement` checkbox type values](/api/reference/constants/#checkbox-field-grouping). - Check out the list of [acceptable `requirement` radio type fields](/api/reference/constants/#radio-field-grouping). - Radio groups require **at least** two fields per group.
            - `groupLabel` (string, optional) — Name of the group
        - `form_fields` (list of object, optional) — An array of Form Field objects containing the name and type of each named field.
          - `type`: `text` (text)
            - `api_id` (string, optional) — A unique id for the form field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the form field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `validation_custom_regex` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the custom regular expression pattern that will be used to validate the text field.
            - `validation_custom_regex_format_label` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the error message displayed to the signer when the text does not match the provided regex pattern.
            - `validation_type` (enum, optional, nullable) — Each text field may contain a `validation_type` parameter. Check out the list of [validation types](https://faq.hellosign.com/hc/en-us/articles/217115577) to learn more about the possible values.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `dropdown` (dropdown)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `hyperlink` (hyperlink)
            - `api_id` (string, optional) — A unique id for the form field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the form field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `radio` (radio)
            - `group` (string, required) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `api_id` (string, optional) — A unique id for the form field.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `signature` (signature)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `date_signed` (date_signed)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `initials` (initials)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `custom_fields` (list of object, optional) — An array of Form Field objects containing the name and type of each named field.
          - `type`: `text` (text)
            - `api_id` (string, optional) — The unique ID for this field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the Custom Field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — The unique ID for this field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the Custom Field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `static_fields` (list of object, optional) — An array describing static overlay fields. **NOTE:** Only available for certain subscriptions.
          - `type`: `text` (text)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `dropdown` (dropdown)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `hyperlink` (hyperlink)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `radio` (radio)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `signature` (signature)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `date_signed` (date_signed)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `initials` (initials)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
      - `accounts` (list of object, optional) — An array of the Accounts that can use this Template.
        - `account_id` (string, optional) — The id of the Account.
        - `email_address` (string, optional) — The email address associated with the Account.
        - `is_locked` (boolean, optional) — Returns `true` if the user has been locked out of their account by a team admin.
        - `is_paid_hs` (boolean, optional) — Returns `true` if the user has a paid Dropbox Sign account.
        - `is_paid_hf` (boolean, optional) — Returns `true` if the user has a paid HelloFax account.
        - `quotas` (object, optional) — An array of the designated CC roles that must be specified when sending a SignatureRequest using this Template.
          - `templates_left` (integer, optional) — API templates remaining.
          - `api_signature_requests_left` (integer, optional) — API signature requests remaining.
          - `documents_left` (integer, optional) — Signature requests remaining.
          - `sms_verifications_left` (integer, optional) — SMS verifications remaining.
      - `attachments` (list of object, optional) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `custom_fields` (list of object, optional, nullable, deprecated) — Deprecated. Use `custom_fields` inside the [documents](https://developers.hellosign.com/api/reference/operation/templateGet/#!c=200&path=template/documents&t=response) array instead.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the Custom Field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the Custom Field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
      - `named_form_fields` (list of object, optional, nullable, deprecated) — Deprecated. Use `form_fields` inside the [documents](https://developers.hellosign.com/api/reference/operation/templateGet/#!c=200&path=template/documents&t=response) array instead.
        - `type`: `text` (text)
          - `api_id` (string, optional) — A unique id for the form field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the form field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `validation_custom_regex` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the custom regular expression pattern that will be used to validate the text field.
          - `validation_custom_regex_format_label` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the error message displayed to the signer when the text does not match the provided regex pattern.
          - `validation_type` (enum, optional, nullable) — Each text field may contain a `validation_type` parameter. Check out the list of [validation types](https://faq.hellosign.com/hc/en-us/articles/217115577) to learn more about the possible values.
            - Allowed values: `numbers_only`, `letters_only`, `phone_number`, `bank_routing_number`, `bank_account_number`, `email_address`, `zip_code`, `social_security_number`, `employer_identification_number`, `custom_regex`
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `hyperlink` (hyperlink)
          - `api_id` (string, optional) — A unique id for the form field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the form field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `radio` (radio)
          - `group` (string, required) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `api_id` (string, optional) — A unique id for the form field.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
  - Template Error Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `template_error`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `template` (object, optional) — Contains information about the templates you and your team have created.
      - `template_id` (string, optional) — The id of the Template.
      - `title` (string, optional) — The title of the Template. This will also be the default subject of the message sent to signers when using this Template to send a SignatureRequest. This can be overridden when sending the SignatureRequest.
      - `message` (string, optional) — The default message that will be sent to signers when using this Template to send a SignatureRequest. This can be overridden when sending the SignatureRequest.
      - `updated_at` (integer, optional) — Time the template was last updated.
      - `is_embedded` (boolean, optional, nullable) — `true` if this template was created using an embedded flow, `false` if it was created on our website. Will be `null` when you are not the creator of the Template.
      - `is_creator` (boolean, optional) — `true` if you are the owner of this template, `false` if it's been shared with you by a team member.
      - `can_edit` (boolean, optional) — Indicates whether edit rights have been granted to you by the owner (always `true` if that's you).
      - `is_locked` (boolean, optional) — Indicates whether the template is locked. If `true`, then the template was created outside your quota and can only be used in `test_mode`. If `false`, then the template is within your quota and can be used to create signature requests.
      - `metadata` (map from string to any, optional) — The metadata attached to the template.
      - `signer_roles` (list of object, optional) — An array of the designated signer roles that must be specified when sending a SignatureRequest using this Template.
        - `name` (string, optional) — The name of the Role.
        - `order` (integer, optional) — If signer order is assigned this is the 0-based index for this role.
      - `cc_roles` (list of object, optional) — An array of the designated CC roles that must be specified when sending a SignatureRequest using this Template.
        - `name` (string, optional) — The name of the Role.
      - `documents` (list of object, optional) — An array describing each document associated with this Template. Includes form field data for each document.
        - `name` (string, optional) — Name of the associated file.
        - `index` (integer, optional) — Document ordering, the lowest index is displayed first and the highest last (0-based indexing).
        - `field_groups` (list of object, optional) — An array of Form Field Group objects.
          - `name` (string, optional) — The name of the form field group.
          - `rule` (object, optional) — The rule used to validate checkboxes in the form field group. See [checkbox field grouping](/api/reference/constants/#checkbox-field-grouping).
            - `requirement` (string, optional) — Examples: `require_0-1` `require_1` `require_1-ormore` - Check out the list of [acceptable `requirement` checkbox type values](/api/reference/constants/#checkbox-field-grouping). - Check out the list of [acceptable `requirement` radio type fields](/api/reference/constants/#radio-field-grouping). - Radio groups require **at least** two fields per group.
            - `groupLabel` (string, optional) — Name of the group
        - `form_fields` (list of object, optional) — An array of Form Field objects containing the name and type of each named field.
          - `type`: `text` (text)
            - `api_id` (string, optional) — A unique id for the form field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the form field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `validation_custom_regex` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the custom regular expression pattern that will be used to validate the text field.
            - `validation_custom_regex_format_label` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the error message displayed to the signer when the text does not match the provided regex pattern.
            - `validation_type` (enum, optional, nullable) — Each text field may contain a `validation_type` parameter. Check out the list of [validation types](https://faq.hellosign.com/hc/en-us/articles/217115577) to learn more about the possible values.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `dropdown` (dropdown)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `hyperlink` (hyperlink)
            - `api_id` (string, optional) — A unique id for the form field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the form field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `radio` (radio)
            - `group` (string, required) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `api_id` (string, optional) — A unique id for the form field.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `signature` (signature)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `date_signed` (date_signed)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `initials` (initials)
            - `api_id` (string, optional) — A unique id for the form field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the form field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional) — The signer of the Form Field.
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `custom_fields` (list of object, optional) — An array of Form Field objects containing the name and type of each named field.
          - `type`: `text` (text)
            - `api_id` (string, optional) — The unique ID for this field.
            - `avg_text_length` (object, optional) — Average text length in this field.
            - `fontFamily` (string, optional) — Font family used in this form field's text.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
            - `name` (string, optional) — The name of the Custom Field.
            - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — The unique ID for this field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this form field.
            - `name` (string, optional) — The name of the Custom Field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
            - `width` (integer, optional) — The width in pixels of this form field.
            - `x` (integer, optional) — The horizontal offset in pixels for this form field.
            - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `static_fields` (list of object, optional) — An array describing static overlay fields. **NOTE:** Only available for certain subscriptions.
          - `type`: `text` (text)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `dropdown` (dropdown)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `hyperlink` (hyperlink)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `checkbox` (checkbox)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `radio` (radio)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `signature` (signature)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `date_signed` (date_signed)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
          - `type`: `initials` (initials)
            - `api_id` (string, optional) — A unique id for the static field.
            - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
            - `height` (integer, optional) — The height in pixels of this static field.
            - `name` (string, optional) — The name of the static field.
            - `required` (boolean, optional) — Boolean showing whether or not this field is required.
            - `signer` (string, optional, default: me_now) — The signer of the Static Field.
            - `width` (integer, optional) — The width in pixels of this static field.
            - `x` (integer, optional) — The horizontal offset in pixels for this static field.
            - `y` (integer, optional) — The vertical offset in pixels for this static field.
      - `accounts` (list of object, optional) — An array of the Accounts that can use this Template.
        - `account_id` (string, optional) — The id of the Account.
        - `email_address` (string, optional) — The email address associated with the Account.
        - `is_locked` (boolean, optional) — Returns `true` if the user has been locked out of their account by a team admin.
        - `is_paid_hs` (boolean, optional) — Returns `true` if the user has a paid Dropbox Sign account.
        - `is_paid_hf` (boolean, optional) — Returns `true` if the user has a paid HelloFax account.
        - `quotas` (object, optional) — An array of the designated CC roles that must be specified when sending a SignatureRequest using this Template.
          - `templates_left` (integer, optional) — API templates remaining.
          - `api_signature_requests_left` (integer, optional) — API signature requests remaining.
          - `documents_left` (integer, optional) — Signature requests remaining.
          - `sms_verifications_left` (integer, optional) — SMS verifications remaining.
      - `attachments` (list of object, optional) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `custom_fields` (list of object, optional, nullable, deprecated) — Deprecated. Use `custom_fields` inside the [documents](https://developers.hellosign.com/api/reference/operation/templateGet/#!c=200&path=template/documents&t=response) array instead.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the Custom Field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null`.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the Custom Field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional, nullable) — The signer of the Custom Field. Can be `null` if field is a merge field (assigned to Sender).
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
      - `named_form_fields` (list of object, optional, nullable, deprecated) — Deprecated. Use `form_fields` inside the [documents](https://developers.hellosign.com/api/reference/operation/templateGet/#!c=200&path=template/documents&t=response) array instead.
        - `type`: `text` (text)
          - `api_id` (string, optional) — A unique id for the form field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the form field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `validation_custom_regex` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the custom regular expression pattern that will be used to validate the text field.
          - `validation_custom_regex_format_label` (string, optional, nullable) — When `validation_type` is set to `custom_regex`, this specifies the error message displayed to the signer when the text does not match the provided regex pattern.
          - `validation_type` (enum, optional, nullable) — Each text field may contain a `validation_type` parameter. Check out the list of [validation types](https://faq.hellosign.com/hc/en-us/articles/217115577) to learn more about the possible values.
            - Allowed values: `numbers_only`, `letters_only`, `phone_number`, `bank_routing_number`, `bank_account_number`, `email_address`, `zip_code`, `social_security_number`, `employer_identification_number`, `custom_regex`
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `hyperlink` (hyperlink)
          - `api_id` (string, optional) — A unique id for the form field.
          - `avg_text_length` (object, optional) — Average text length in this field.
            - `num_lines` (integer, optional) — Number of lines.
            - `num_chars_per_line` (integer, optional) — Number of characters per line.
          - `fontFamily` (string, optional) — Font family used in this form field's text.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `isMultiline` (boolean, optional) — Whether this form field is multiline text.
          - `name` (string, optional) — The name of the form field.
          - `originalFontSize` (integer, optional) — Original font size used in this form field's text.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `radio` (radio)
          - `group` (string, required) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `api_id` (string, optional) — A unique id for the form field.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — A unique id for the form field.
          - `group` (string, optional, nullable) — The name of the group this field is in. If this field is not a group, this defaults to `null` except for Radio fields.
          - `height` (integer, optional) — The height in pixels of this form field.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — Boolean showing whether or not this field is required.
          - `signer` (string, optional) — The signer of the Form Field.
          - `width` (integer, optional) — The width in pixels of this form field.
          - `x` (integer, optional) — The horizontal offset in pixels for this form field.
          - `y` (integer, optional) — The vertical offset in pixels for this form field.
  - Sign URL Invalid Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `sign_url_invalid`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.
    - `signature_request` (object, optional) — Contains information about a signature request.
      - `test_mode` (boolean, optional, default: false) — Whether this is a test signature request. Test requests have no legal value. Defaults to `false`.
      - `signature_request_id` (string, optional) — The id of the SignatureRequest.
      - `requester_email_address` (string, optional, nullable) — The email address of the initiator of the SignatureRequest.
      - `title` (string, optional) — The title the specified Account uses for the SignatureRequest.
      - `original_title` (string, optional) — Default Label for account.
      - `subject` (string, optional, nullable) — The subject in the email that was initially sent to the signers.
      - `message` (string, optional, nullable) — The custom message in the email that was initially sent to the signers.
      - `metadata` (map from string to any, optional) — The metadata attached to the signature request.
      - `created_at` (integer, optional) — Time the signature request was created.
      - `expires_at` (integer, optional, nullable) — The time when the signature request will expire unsigned signatures. See [Signature Request Expiration Date](https://developers.hellosign.com/docs/signature-request/expiration/) for details.
      - `is_complete` (boolean, optional) — Whether or not the SignatureRequest has been fully executed by all signers.
      - `is_declined` (boolean, optional) — Whether or not the SignatureRequest has been declined by a signer.
      - `has_error` (boolean, optional) — Whether or not an error occurred (either during the creation of the SignatureRequest or during one of the signings).
      - `files_url` (string, optional) — The URL where a copy of the request's documents can be downloaded.
      - `signing_url` (string, optional, nullable) — The URL where a signer, after authenticating, can sign the documents. This should only be used by users with existing Dropbox Sign accounts as they will be required to log in before signing.
      - `details_url` (string, optional) — The URL where the requester and the signers can view the current status of the SignatureRequest.
      - `cc_email_addresses` (list of string, optional) — A list of email addresses that were CCed on the SignatureRequest. They will receive a copy of the final PDF once all the signers have signed.
      - `signing_redirect_url` (string, optional, nullable) — The URL you want the signer redirected to after they successfully sign.
      - `final_copy_uri` (string, optional, nullable) — The path where the completed document can be downloaded
      - `template_ids` (list of string, optional, nullable) — Templates IDs used in this SignatureRequest (if any).
      - `custom_fields` (list of object, optional, nullable) — An array of Custom Field objects containing the name and type of each custom field. * Text Field uses `SignatureRequestResponseCustomFieldText` * Checkbox Field uses `SignatureRequestResponseCustomFieldCheckbox`
        - `type`: `text` (text)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (string, optional) — A text string for text fields
        - `type`: `checkbox` (checkbox)
          - `name` (string, required) — The name of the Custom Field.
          - `api_id` (string, optional) — The unique ID for this field.
          - `editor` (string, optional, nullable) — The name of the Role that is able to edit this field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
          - `value` (boolean, optional) — A true/false for checkbox fields
      - `attachments` (list of object, optional, nullable) — Signer attachments.
        - `id` (string, required) — The unique ID for this attachment.
        - `signer` (string, required) — The Signer this attachment is assigned to.
        - `name` (string, required) — The name of this attachment.
        - `required` (boolean, required) — A boolean value denoting if this attachment is required.
        - `instructions` (string, optional, nullable) — Instructions for Signer.
        - `uploaded_at` (integer, optional, nullable) — Timestamp when attachment was uploaded by Signer.
      - `response_data` (list of object, optional, nullable) — An array of form field objects containing the name, value, and type of each textbox or checkmark field filled in by the signers.
        - `type`: `text` (text)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox` (checkbox)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `dropdown` (dropdown)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `radio` (radio)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `signature` (signature)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `date_signed` (date_signed)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `initials` (initials)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `text-merge` (text-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
        - `type`: `checkbox-merge` (checkbox-merge)
          - `api_id` (string, optional) — The unique ID for this field.
          - `signature_id` (string, optional) — The ID of the signature to which this response is linked.
          - `name` (string, optional) — The name of the form field.
          - `required` (boolean, optional) — A boolean value denoting if this field is required.
      - `signatures` (list of object, optional) — An array of signature objects, 1 for each signer.
        - `signature_id` (string, optional) — Signature identifier.
        - `signer_group_guid` (string, optional, nullable) — Signer Group GUID
        - `signer_email_address` (string, optional) — The email address of the signer.
        - `signer_name` (string, optional, nullable) — The name of the signer.
        - `signer_role` (string, optional, nullable) — The role of the signer.
        - `order` (integer, optional, nullable) — If signer order is assigned this is the 0-based index for this signer.
        - `status_code` (string, optional) — The current status of the signature. eg: awaiting_signature, signed, declined.
        - `decline_reason` (string, optional, nullable) — The reason provided by the signer for declining the request.
        - `signed_at` (integer, optional, nullable) — Time that the document was signed or null.
        - `last_viewed_at` (integer, optional, nullable) — The time that the document was last viewed by this signer or null.
        - `last_reminded_at` (integer, optional, nullable) — The time the last reminder email was sent to the signer or null.
        - `has_pin` (boolean, optional) — Boolean to indicate whether this signature requires a PIN to access.
        - `has_sms_auth` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS authentication enabled.
        - `has_sms_delivery` (boolean, optional, nullable) — Boolean to indicate whether this signature has SMS delivery enabled.
        - `sms_phone_number` (string, optional, nullable) — The SMS phone number used for authentication or signature request delivery.
        - `reassigned_by` (string, optional, nullable) — Email address of original signer who reassigned to this signer.
        - `reassignment_reason` (string, optional, nullable) — Reason provided by original signer who reassigned to this signer.
        - `reassigned_from` (string, optional, nullable) — Previous signature identifier.
        - `error` (string, optional, nullable) — Error message pertaining to this signer, or null.
      - `bulk_send_job_id` (string, optional, nullable) — The ID of the Bulk Send job which sent the signature request, if applicable.
  - Callback Test Event
    - `event` (object, required) — Basic information about the event that occurred.
      - `event_time` (string, required) — Time the event was created (using Unix time).
      - `event_type` (enum, required) — Type of callback event that was triggered.
        - Allowed values: `callback_test`
      - `event_hash` (string, required) — Generated hash used to verify source of event data.
      - `event_metadata` (object, optional) — Specific metadata about the event.
        - `related_signature_id` (string, optional, nullable) — Signature ID for a specific signer. Applicable to `signature_request_signed` and `signature_request_viewed` events.
        - `reported_for_account_id` (string, optional, nullable) — Account ID the event was reported for.
        - `reported_for_app_id` (string, optional, nullable) — App ID the event was reported for.
        - `event_message` (string, optional, nullable) — Message about a declined or failed (due to error) signature flow.