AP2 — Agent Payments Protocol Documentation
by Google
The open spec for letting an agent spend money for a user — and cryptographically prove it was authorized.
Overview
The site is short and dense: an Executive Summary, a seven-part Specification (Agent Payments Protocol, Agent Authorization Framework, Flows, Checkout Mandate, Payment Mandate, Security and Privacy Considerations, Implementation Considerations), a Glossary, an FAQ, and five sample scenarios. The core idea is the mandate — a tamper-evident, cryptographically signed Verifiable Digital Credential recording what the user actually authorized. The specification organises these into a Checkout Mandate shared with the merchant and a Payment Mandate shared with the credential provider, each in an open form carrying the constraints the agent must stay inside and a closed form authorizing a finalized transaction; the original launch framing of Intent, Cart and Payment mandates maps onto the same structure. Two flows are specified: human-present, where the user signs off on a cart the agent has assembled, and human-not-present, where a pre-signed mandate with price and timing limits lets the agent execute later without the user in the loop. AP2 is deliberately payment-method-agnostic — cards, real-time bank transfers and stablecoins, with an A2A x402 extension built alongside Coinbase, the Ethereum Foundation and MetaMask — and is positioned as an extension to Agent2Agent that is compatible with the Model Context Protocol rather than a replacement for either. The reference repository (Apache-2.0, roughly 3.1K stars) carries a Python SDK of Pydantic models and JSON schemas plus runnable scenarios in Python, Go and Android.
At a Glance
- Topic
- Agentic
- Level
- Intermediate
- Format
- Documentation
- Cost
- Free
- Duration
- ~2-3 hours to read the specification end to end; about a day to run the reference samples
- Provider
- Hands-on
- Yes — code/exercises
- Certificate
- None
What You’ll Learn
- ✓How a mandate encodes user authorization as a signed verifiable digital credential
- ✓The difference between the open and closed forms of Checkout and Payment mandates
- ✓Designing a human-present checkout flow where the user signs the finalized cart
- ✓Designing a human-not-present flow with pre-signed price and timing constraints
- ✓Which actor holds which credential, and why payment details stay off the merchant path
- ✓How AP2 layers onto Agent2Agent and coexists with Model Context Protocol tool calls
- ✓The accountability chain the specification defines when an agent transacts wrongly
- ✓Running the Python, Go or Android reference scenarios against the published JSON schemas
Highlights
- •A rare agent specification that treats proof of authorization as the primary artifact rather than an afterthought
- •Payment-method-agnostic by construction — the same mandate flow covers cards, real-time bank transfers and stablecoins via the x402 extension
- •Backed at launch by 60+ organizations including Mastercard, American Express, PayPal, Adyen, Coinbase, Etsy and Salesforce, so it is not a single-vendor spec
- •Reference implementations in three languages with runnable local scenarios, not just prose
- •Explicitly an extension of A2A and compatible with MCP, so it slots into an existing agent stack instead of replacing it
Who It’s For
Best For
- ✓Engineers building agents that purchase, book or transact autonomously
- ✓Payments and fintech teams assessing how agentic checkout reaches them
- ✓Architects already using A2A or MCP who need an authorization layer
- ✓Security engineers evaluating accountability for autonomous spending
Prerequisites
- •Understanding of agent-to-agent messaging, ideally the A2A protocol
- •Familiarity with verifiable credentials and public-key signatures
- •Helpful: working knowledge of card or crypto payment flows
FAQ
What is AP2 — Agent Payments Protocol Documentation?
AP2 is an open protocol, launched by Google in September 2025 with more than 60 payment and commerce partners, that defines how an AI agent can transact on a user's behalf with verifiable proof of authorization. This documentation is for engineers building agentic commerce: it specifies the mandate credentials, the authorization framework, the transaction flows and the security model, and ships runnable reference implementations in three languages.
Is AP2 — Agent Payments Protocol Documentation free?
AP2 — Agent Payments Protocol Documentation is free to access.
What level is AP2 — Agent Payments Protocol Documentation for?
AP2 — Agent Payments Protocol Documentation is aimed at a intermediate audience. Recommended background: Understanding of agent-to-agent messaging, ideally the A2A protocol, Familiarity with verifiable credentials and public-key signatures, Helpful: working knowledge of card or crypto payment flows.
How long does AP2 — Agent Payments Protocol Documentation take?
Expect roughly ~2-3 hours to read the specification end to end; about a day to run the reference samples. Most learners work through it at their own pace.
What will I learn from AP2 — Agent Payments Protocol Documentation?
You'll learn: How a mandate encodes user authorization as a signed verifiable digital credential; The difference between the open and closed forms of Checkout and Payment mandates; Designing a human-present checkout flow where the user signs the finalized cart; Designing a human-not-present flow with pre-signed price and timing constraints; Which actor holds which credential, and why payment details stay off the merchant path; How AP2 layers onto Agent2Agent and coexists with Model Context Protocol tool calls; The accountability chain the specification defines when an agent transacts wrongly; Running the Python, Go or Android reference scenarios against the published JSON schemas.
Topics
Sources
This page was written from 3 sources, 2 on domains other than ap2-protocol.org.