Clickatell External Link Callback API

openapi: 3.2.0
info:
  title: Flow External Link Callback API
  version: 1.1.0
  x-provenance:
    method: searched
    source: https://help.clickatell.com/developers-api-reference/ (OpenAPI fragments embedded verbatim in the GitBook .md twins, merged by info.title)
    generated: '2026-10-13'
servers:
- url: https://flow-callback.clickatell.com/
  description: Production server
- url: https://control-callback-uat.payd.co/
  description: Sandbox/UAT server
tags:
- name: External Link Callback
paths:
  /callback:
    post:
      tags:
      - External Link Callback
      summary: Direct an end-user to an external web page
      description: 'The External Link Handler API allows you to direct an end-user to an external web page from within a Flow conversation and then return to the Flow conversation with optional additional data gathered from the external web page.


        The end-user can then continue with the conversational workflow according to the steps defined in Flow.'
      parameters:
      - name: reference
        in: header
        description: A reference to be passed as a header. This value is also required in the body section, please refer accordingly for the description.
        required: true
        schema:
          type: string
      requestBody:
        description: Payload describing the external link
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/Externallink'
        required: true
      responses:
        '200':
          description: Successfully validated the response and returned data appended to matched session.
          content: {}
        '400':
          description: A bad/invalid reference was returned and the session could not be matched
          content: {}
      operationId: postCallback
      x-operation-id-source: derived
components:
  schemas:
    Externallink:
      required:
      - result
      type: object
      properties:
        result:
          type: string
          description: Used to evaluate success or failure in Flow and can be any value you wish to return for evaluation
        reference:
          type: string
          description: 'A unique hash generated by Flow based on SessionID and SourceID that allows us to identify the user''s session. This value is automatically appended as a query parameter on external links and should be intercepted and returned with the callback for validation (in header and body): e.g. `https://www.example.com?reference=f7_4hn5=8f&%#nK=`'
        data:
          type: object
          additionalProperties:
            type: string
          description: An optional hashmap with any key and value that can be referenced in the flow later on.