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

# Register a webhook subscription

> Register a webhook endpoint to receive push events for subscribed event types, starting with `discovery.revision` (progressive discovery updates — see the SSE-equivalent `GET /discovery/{discoveryId}/events`). Deliveries are HMAC-SHA256 signed with the provided secret in the `X-Webhook-Signature` header.



## OpenAPI

````yaml /v2/buyer-api-v2.yaml post /webhook-subscriptions
openapi: 3.0.0
info:
  title: Scope3 Buyer API
  version: 2.0.0
  description: |-
    REST API for advertisers to manage advertisers, campaigns, and reporting.

    ## Authentication

    All endpoints require a Bearer token in the Authorization header:
    ```
    Authorization: Bearer your-api-key
    ```

    ## Base URL

    `https://api.interchange.io/api/v2/buyer`

    ## For AI Agents

    AI agents can use the MCP endpoint at `/mcp/v2/buyer` with three tools:
    - `initialize`: Start an MCP session
    - `api_call`: Make REST API calls
    - `ask_about_capability`: Learn about API features
servers:
  - url: https://api.interchange.io/api/v2/buyer
    description: Production server
security: []
tags:
  - name: Account
    description: Account management, service tokens, and preferences
  - name: Advertisers
    description: Manage advertisers
  - name: Product Discovery
    description: Discover and select products
  - name: Campaigns
    description: Manage advertising campaigns
  - name: Creatives
    description: Build, manage, and sync campaign creatives via AdCP Creative Protocol
  - name: Reporting
    description: Access performance metrics
  - name: Event Sources
    description: >-
      Manage event source configurations and log conversion/marketing events for
      attribution
  - name: Property Lists
    description: Validate property lists against AAO registry
  - name: Sales Agents
    description: View and connect sales agents
  - name: Measurement
    description: Measurement sources, records, context, and freshness
  - name: Syndication
    description: Syndicate resources to ADCP agents
  - name: Tasks
    description: Track async operation status
  - name: Planning Briefs
    description: >-
      Share prospective briefs with publishers and collect their
      fit/quote/clarify/decline/book responses (gated by the
      demand-supply-signals flag).
  - name: Buyer Billing
    description: >-
      Consolidated invoicing for buyers — invoices and pending invoice items
      issued by Scope3 across the buyer customer.
  - name: MCP
    description: Model Context Protocol endpoints for AI agents
paths:
  /webhook-subscriptions:
    post:
      tags:
        - Webhook Subscriptions
      summary: Register a webhook subscription
      description: >-
        Register a webhook endpoint to receive push events for subscribed event
        types, starting with `discovery.revision` (progressive discovery updates
        — see the SSE-equivalent `GET /discovery/{discoveryId}/events`).
        Deliveries are HMAC-SHA256 signed with the provided secret in the
        `X-Webhook-Signature` header.
      operationId: createWebhookSubscription
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                url:
                  type: string
                  maxLength: 2048
                  format: uri
                secret:
                  type: string
                  minLength: 16
                  maxLength: 256
                eventTypes:
                  minItems: 1
                  type: array
                  items:
                    type: string
                    enum:
                      - discovery.revision
              required:
                - url
                - secret
                - eventTypes
      responses:
        '201':
          description: Register a webhook subscription
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/BuyerWebhookSubscriptionResponse'
        '400':
          description: Bad request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
      security:
        - bearerAuth: []
components:
  schemas:
    BuyerWebhookSubscriptionResponse:
      type: object
      properties:
        subscription:
          $ref: '#/components/schemas/BuyerWebhookSubscription'
      required:
        - subscription
      additionalProperties: false
    ErrorResponse:
      description: Standard error response
      type: object
      properties:
        data:
          type: string
          nullable: true
          enum:
            - null
        error:
          $ref: '#/components/schemas/ApiError'
      required:
        - data
        - error
      additionalProperties: false
    BuyerWebhookSubscription:
      type: object
      properties:
        id:
          type: string
        url:
          type: string
        eventTypes:
          type: array
          items:
            type: string
            enum:
              - discovery.revision
        status:
          type: string
          enum:
            - active
            - inactive
            - failed
        failureCount:
          type: integer
          minimum: 0
          maximum: 9007199254740991
        lastSuccess:
          nullable: true
          type: string
        lastFailure:
          nullable: true
          type: string
        createdAt:
          type: string
        updatedAt:
          type: string
      required:
        - id
        - url
        - eventTypes
        - status
        - failureCount
        - lastSuccess
        - lastFailure
        - createdAt
        - updatedAt
      additionalProperties: false
    ApiError:
      description: Structured error object
      type: object
      properties:
        code:
          description: Machine-readable error code
          type: string
        message:
          description: Human-readable error message
          type: string
        field:
          description: Field path associated with the error
          type: string
        details:
          description: Additional error context
          type: object
          additionalProperties: {}
      required:
        - code
        - message
      additionalProperties: false
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: API key or access token

````