Google Pay Authentication

specification: API Commons Authentication
specificationVersion: '0.1'
provider: Google Pay
providerId: google-pay
generated: '2026-09-12'
method: searched
source: >-
  https://developers.google.com/pay/api/web/guides/setup ·
  https://developers.google.com/pay/api/web/guides/test-and-deploy/deploy-production-environment ·
  https://developers.google.com/wallet/generic/rest/prerequisites ·
  https://developers.google.com/pay/api/web/guides/use-pay-wallet-mcp ·
  well-known/google-pay-accounts-openid-configuration.json (probed 2026-09-12)
note: >-
  derive-authentication.py found no securitySchemes because Google publishes no OpenAPI for any
  Google Pay surface. This profile was read from Google's own setup and prerequisite pages and
  from the live OpenID discovery document at accounts.google.com. There is no single Google Pay
  auth model — the surfaces authenticate four different ways, which is the finding.
schemes:
  - id: merchant-registration
    applies_to:
      - Google Pay API (Web)
      - Google Pay API for Android
    type: none
    description: >-
      The Google Pay Web and Android client APIs carry no bearer credential at all. Authorisation
      is an out-of-band merchant registration: a Google Pay Business Profile is created in the
      Google Pay & Wallet Console, the top-level domain calling the API is registered against it,
      the Google Pay API Terms of Service and Acceptable Use Policy are accepted, integration
      screenshots are submitted for Google review, and only after approval may the client pass
      environment PRODUCTION with a real merchantId in MerchantInfo.
    credential_fields:
      - merchantId
      - merchantName
    environments:
      - TEST
      - PRODUCTION
    docs: https://developers.google.com/pay/api/web/guides/test-and-deploy/deploy-production-environment
  - id: payment-token-cryptography
    applies_to:
      - Google Pay API (Web)
      - Google Pay API for Android
    type: message-signing
    description: >-
      Returned payment data is a signed and encrypted PaymentMethodToken. Google signs the token
      with its own keys and encrypts to the merchant's or gateway's public key using ECIES
      (Elliptic Curve Integrated Encryption Scheme). Protocol versions ECv1 and ECv2; ECv2 is the
      default for new integrations. Direct (non-gateway) integration requires the merchant to be
      PCI DSS compliant as validated by a Qualified Security Assessor.
    key_material:
      test_signing_keys: https://payments.developers.google.com/paymentmethodtoken/test/keys.json
    docs: https://developers.google.com/pay/api/web/guides/resources/payment-data-cryptography
  - id: oauth2-service-account
    applies_to:
      - Google Wallet API
    type: oauth2
    flows:
      - jwt-bearer (Google service account)
    scopes:
      - https://www.googleapis.com/auth/wallet_object.issuer
    token_endpoint: https://oauth2.googleapis.com/token
    issuer: https://accounts.google.com
    description: >-
      Google Wallet REST calls against walletobjects.googleapis.com are authorised with a Google
      Cloud service account key exchanged for an OAuth 2.0 access token. The single scope is the
      one declared in the Wallet API Discovery document.
    evidence: discovery/google-pay-walletobjects-v1-discovery.json (auth.oauth2.scopes)
    docs: https://developers.google.com/wallet/generic/rest/prerequisites
  - id: oauth2-mcp
    applies_to:
      - Google Pay & Wallet Developer MCP server
    type: oauth2
    flows:
      - authorization_code
    scopes:
      - https://www.googleapis.com/auth/paydeveloper.merchant
      - https://www.googleapis.com/auth/paydeveloper.issuer.readonly
    iam_role: roles/mcp.toolUser
    api_keys_accepted: false
    issuer: https://accounts.google.com
    description: >-
      The MCP server at paydeveloper.googleapis.com authenticates with OAuth 2.0 client
      credentials plus Google Cloud IAM. Google states explicitly that the server does not accept
      API keys. tools/list is readable anonymously; tool invocation is not.
    docs: https://developers.google.com/pay/api/web/guides/use-pay-wallet-mcp
  - id: ucp-profile-signing
    applies_to:
      - Google Universal Commerce Protocol
    type: message-signing
    algorithm: ES256
    description: >-
      Google's UCP discovery profile at ucp.goog publishes four ES256 (P-256) JWK signing keys in
      both a signing_keys[] and a keys[] array, used to verify UCP payloads exchanged with
      Google's commerce surfaces.
    evidence: well-known/google-pay-ucp-profile.json
    docs: https://developers.google.com/merchant/ucp/guides/ucp-profile
authorization_server:
  issuer: https://accounts.google.com
  openid_configuration: https://accounts.google.com/.well-known/openid-configuration
  oauth_authorization_server: https://accounts.google.com/.well-known/oauth-authorization-server
  probed: '2026-09-12'
  http_status: 200
  files:
    - well-known/google-pay-accounts-openid-configuration.json
    - well-known/google-pay-accounts-oauth-authorization-server.json