> ## 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.

# Start adding a card (admin)

> Create a card-capture session for the organization and return the client secret the embedded card form needs, plus the publishable key to mount it. The saved method appears (via webhook-verified confirmation) in the payment-methods list and on the billing-account document; it is never inferred from the client-side confirmation alone. Org-admin humans only — service tokens are denied. 403 FEATURE_NOT_ENABLED until the buyer-card-collection flag is on for the organization.



## OpenAPI

````yaml /v2/buyer-api-v2.yaml post /billing/payment-methods/setup
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:
  /billing/payment-methods/setup:
    servers:
      - url: https://api.interchange.io/api/v2
        description: Production server
    post:
      tags:
        - Buyer Billing
      summary: Start adding a card (admin)
      description: >-
        Create a card-capture session for the organization and return the client
        secret the embedded card form needs, plus the publishable key to mount
        it. The saved method appears (via webhook-verified confirmation) in the
        payment-methods list and on the billing-account document; it is never
        inferred from the client-side confirmation alone. Org-admin humans only
        — service tokens are denied. 403 FEATURE_NOT_ENABLED until the
        buyer-card-collection flag is on for the organization.
      operationId: setupPaymentMethod
      responses:
        '200':
          description: Start adding a card (admin)
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SetupPaymentMethodResponse'
        '400':
          description: Bad request
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '401':
          description: Unauthorized
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
        '403':
          description: >-
            FEATURE_NOT_ENABLED (flag off) or ACCESS_DENIED (not an org admin,
            or a service token).
          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:
    SetupPaymentMethodResponse:
      description: >-
        Everything the client needs to mount an embedded card-capture form. The
        resulting payment method is NOT returned here — it appears once the card
        rail webhook confirms it (spec §6: never inferred from a client
        callback).
      type: object
      properties:
        clientSecret:
          description: >-
            The capture-session client secret. The UI passes this to the
            embedded card form (no redirect) to collect and confirm the card.
          type: string
        publishableKey:
          description: >-
            The card rail's publishable key, for mounting the embedded card form
            client-side. Not secret.
          type: string
      required:
        - clientSecret
        - publishableKey
      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
    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

````