# Google Pay > Google Pay is Google's digital wallet and payment surface. For developers it is not one API but > a family: a client-side JavaScript / Android payment sheet that returns an encrypted payment > token, a Google-standard REST API for issuing Google Wallet passes, a set of Google Standard > Payments integrator APIs for issuers and PSPs, and — since 2026 — a remote MCP server for > developer and merchant-console operations. Generated: 2026-09-12 Method: generated (from apis.yml and the artifacts in this repository; no /llms.txt is published by Google — probed developers.google.com/llms.txt, developers.google.com/pay/llms.txt and pay.google.com/llms.txt on 2026-09-12, all 404) Source: https://github.com/api-evangelist/google-pay ## What an agent can actually call - **MCP server (remote, OAuth):** https://paydeveloper.googleapis.com/mcp — 13 tools. `tools/list` answers anonymously; tool calls need OAuth 2.0 + the IAM role `roles/mcp.toolUser`. Google states it does not accept API keys. - **Google Wallet REST API:** https://walletobjects.googleapis.com/ — 99 methods, machine-readable as a Google API Discovery document, OAuth 2.0 service account, scope `https://www.googleapis.com/auth/wallet_object.issuer`. - **Google Pay Web / Android:** not callable by an agent. It is a shopper-facing payment sheet invoked from a browser or Android app; there is no server endpoint. ## Machine-readable contracts - MCP tool manifest (verbatim): mcp/google-pay-mcp-tools-list.json - Google Wallet API Discovery document (verbatim, rev 20260911): discovery/google-pay-walletobjects-v1-discovery.json - Google Pay UCP payment-handler config schema, JSON Schema 2020-12 (verbatim): json-schema/google-pay-ucp-payment-handler-config.json - Google's Universal Commerce Protocol profile (verbatim): well-known/google-pay-ucp-profile.json - **There is no OpenAPI.** Google publishes none for any Google Pay surface. Probed the API host roots, the docs host and the MCP host on 2026-09-12. ## APIs - [Google Pay API (Web)](https://developers.google.com/pay/api/web) — JavaScript PaymentsClient; returns a signed, ECIES-encrypted PaymentMethodToken. - [Google Pay API for Android](https://developers.google.com/pay/api/android/overview) — PaymentsClient via Google Play services. - [Google Wallet API](https://developers.google.com/wallet) — loyalty, event tickets, boarding passes, transit, gift cards, offers, generic passes. - [Google Pay & Wallet Developer MCP server](https://developers.google.com/pay/api/web/guides/use-pay-wallet-mcp) - [Facilitated Transaction Event API](https://developers.google.com/pay/facilitated-transaction-event-v2/concepts/intro) - [Virtual Cards API](https://developers.google.com/pay/virtual-cards-v1/payment-integrator-virtual-cards-api) - [Push Provisioning API](https://developers.google.com/pay/issuers/apis/push-provisioning/server) - [Payment Card Recognition API](https://developers.google.com/pay/payment-card-recognition/debit-credit-card-recognition) - [Google Pay India Merchant SDK](https://developers.google.com/pay/india/api) - [Universal Commerce Protocol](https://developers.google.com/merchant/ucp) — Google's UCP profile is served at https://ucp.goog/.well-known/ucp.json ## Authentication Four different models, one per surface. Merchant registration + registered domain for the client APIs (no bearer token at all); OAuth 2.0 service account for Wallet REST; OAuth 2.0 + Cloud IAM for MCP; ES256 message signing for UCP. See authentication/google-pay-authentication.yml and scopes/google-pay-scopes.yml. ## Things an agent should know before integrating - **No idempotency.** No Idempotency-Key, no client request id, no replay-safe retry contract on any surface. Do not blind-retry a write. (conventions/google-pay-conventions.yml) - **No rate-limit headers.** Google publishes one number — 20 requests/second for the Google Wallet API — in a FAQ paragraph, and no runtime header or exhaustion status code anywhere. - **No deprecation policy and no SLA.** Changes arrive as dated release notes with no stated window and no Sunset/Deprecation headers. - **Production access is human-gated.** A Google Pay Business Profile, accepted Terms and Acceptable Use Policy, a registered top-level domain, and screenshots reviewed by the Google Pay team. TEST needs none of that. - **No fee.** "Google Pay doesn't additionally charge users, merchants, and developers additional fees to use the Google Pay API for payments." Processing fees are your PSP's. - **Decline codes are not Google's.** Google Pay is a wallet, not an acquirer; authorisation outcomes come from your gateway after it decrypts the token. ## Errors `PaymentsError { statusCode, statusMessage }` on the client APIs. Four documented codes: BUYER_ACCOUNT_ERROR, DEVELOPER_ERROR, MERCHANT_ACCOUNT_ERROR, INTERNAL_ERROR. Only the last is worth retrying. https://developers.google.com/pay/api/web/reference/error-objects ## Testing `environment: 'TEST'` on the PaymentsClient constructor — same host, no separate key. Gateway test cards for 24+ gateways, mock PAN_ONLY cards otherwise, sample tokens signed with Google's test keys at https://payments.developers.google.com/paymentmethodtoken/test/keys.json. See sandbox/google-pay-sandbox.yml. ## First-party packages @google-pay/button-element, @google-pay/button-react, @google-pay/button-angular (npm, 4.1.0, 2026-08-24) · pay (pub.dev, 3.3.0, 2025-11-21) · com.google.pay.button:compose-pay-button (Maven Central, 1.1.0, 2025-01-06) · react-native-make-payment (GitHub only, no npm release). See packages/google-pay-packages.yml. ## Links - Developer portal: https://developers.google.com/pay - Google Pay & Wallet Console: https://pay.google.com/business/console/ - Status dashboard: https://developers.google.com/pay/api/status - Release notes: https://developers.google.com/pay/api/web/support/release-notes - Troubleshooting: https://developers.google.com/pay/api/web/support/troubleshooting - FAQ: https://developers.google.com/pay/api/faq - Brand guidelines: https://developers.google.com/pay/api/web/guides/brand-guidelines - Terms of Service: https://payments.developers.google.com/terms/sellertos - GitHub: https://github.com/google-pay - Security / VDP: https://g.co/vrp (https://www.google.com/.well-known/security.txt)