> ## Documentation Index
> Fetch the complete documentation index at: https://www.bolna.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Get callback URL API

> Fetch a workflow callback node's inbound URL and signing secret, so your system knows where to POST results and how to sign them.



## OpenAPI

````yaml GET /workflows/{workflow_id}/nodes/{node_id}/callback
openapi: 3.1.0
info:
  title: Bolna API
  description: >-
    Use and leverage Bolna Voice AI using APIs through HTTP requests from any
    language in your applications and workflows.
  license:
    name: MIT
  version: 1.0.0
servers:
  - url: https://api.bolna.ai
    description: Production server
security:
  - bearerAuth: []
tags:
  - name: SIP trunks
    description: >-
      Bring-your-own-carrier SIP trunks, their gateways, carrier IPs and
      numbers.
paths:
  /workflows/{workflow_id}/nodes/{node_id}/callback:
    get:
      description: >
        Returns a callback node's live inbound URL, with its slug and the secret
        your system signs requests with. A URL is minted the first time the node
        is saved in a draft, or on the first read if it has none yet.


        The URL stays the same across renames and publishes. Replace it with the
        [Rotate Callback URL API](/api-reference/workflows/rotate-callback). See
        [Callback node](/workflows/callback) for the request your system sends
        to it.
      parameters:
        - in: path
          name: workflow_id
          required: true
          schema:
            type: string
            format: uuid
          description: The unique `id` of the workflow
        - in: path
          name: node_id
          required: true
          schema:
            type: string
          description: >-
            The `id` of a callback node in the workflow's draft or in its latest
            published version
      responses:
        '200':
          description: The node's live callback URL
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/WorkflowCallbackEndpoint'
        '404':
          description: Workflow not found, or it has no callback node with this id
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/WorkflowError'
components:
  schemas:
    WorkflowCallbackEndpoint:
      type: object
      required:
        - url
        - slug
        - signing_secret
        - created_at
      properties:
        url:
          type: string
          format: uri
          description: The URL your system POSTs to.
          example: https://hooks.bolna.ai/callbacks/Zr0x3M5uQ8lA2wq7Yb1nC4dE6fG9hJkL
        slug:
          type: string
          description: The URL's final path segment.
          example: Zr0x3M5uQ8lA2wq7Yb1nC4dE6fG9hJkL
        signing_secret:
          type: string
          description: >-
            A 64-character hex string. Use it as the literal ASCII key for the
            `X-Bolna-Signature` HMAC; don't hex-decode it.
          example: 9b1f0c7e5a3d2b4c6e8f0a1b3c5d7e9f1a2b4c6d8e0f1a3b5c7d9e1f2a4b6c8d
        created_at:
          type: string
          format: date-time
          description: When this URL was issued.
        rate_limit_per_min:
          type: integer
          nullable: true
          description: >-
            Requests per minute this URL accepts before answering `429`. `null`
            means the default of 1000.
    WorkflowError:
      type: object
      description: >-
        Error envelope returned by every workflow endpoint. `detail.code` is a
        stable machine-readable code; extra keys (such as `current_revision` on
        `revision_conflict`, `execution_id` on `duplicate_run`, or `issues` on
        `invalid_definition`) ride alongside it.
      required:
        - detail
      properties:
        detail:
          type: object
          additionalProperties: true
          required:
            - code
            - message
          properties:
            code:
              type: string
              description: Machine-readable error code.
              example: revision_conflict
            message:
              type: string
              description: Human-readable explanation.
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer

````

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