ap2

# AP2 — Agent Payments Protocol ## Overview AP2 is an open protocol from Google for secure, interoperable AI-driven commerce. It provides a common language for transactions between agents and merchants, preventing a fragmented payments ecosystem. AP2 is designed as an extension for A2A and MCP, adding a secure commerce layer on top of agent communication. ## Core Concepts ### Intent Mandate Captures the conditions under which an AI agent can make a purchase on behalf of the user: - Budget limits (per-transaction, daily, monthly) - Allowed merchant categories - Product type restrictions - Time-based constraints ### Cart Mandate Captures the user's final, explicit authorization for a specific cart: - Itemized list of products/services - Total price and currency - User's cryptographic signature (non-repudiable proof of intent) - Payment method reference ## Payment Flow ``` User Agent Merchant Payment Provider │ │ │ │ │── "Buy X" ───►│ │ │ │ │── browse ─────►│ │ │ │◄── product ────│ │ │ │ │ │ │◄── confirm? ──│ │ │ │── approve ───►│ (Cart Mandate signed) │ │ │── purchase ───►│ │ │ │ │── charge ───────►│ │ │ │◄── receipt ──────│ │ │◄── receipt ────│ │ │◄── done ──────│ │ │ ``` ## Key Design Principles | Principle | Description | |-----------|-------------| | **User control** | Users set spending limits and approve purchases via signed mandates | | **Verifiable credentials** | Cryptographic signatures provide non-repudiable proof of authorization | | **Protocol-agnostic payments** | Supports pull methods (credit/debit cards) initially, with push methods (bank transfers, wallets) planned | | **Compliant by design** | Built-in support for regulatory requirements (PCI, PSD2) | ## Phased Rollout | Version | Scope | |---------|-------| | v0.1 | Core architecture, pull payment methods (credit/debit cards) | | Future | Push payments, real-time bank transfers, e-wallets, multi-currency | ## AP2 vs x402 | Aspect | AP2 | x402 | |--------|-----|------| | Focus | Full commerce flow (browse → buy → receipt) | Per-request API micropayments | | Payment methods | Cards, bank transfers, wallets | Stablecoins (USDC on Base/Solana) | | Authorization | Intent + Cart Mandates with user signatures | Wallet-signed HTTP headers | | Use case | Agent-driven shopping and purchases | Monetizing APIs and content | | Relationship | Extension for A2A/MCP | Standalone HTTP protocol | ## Integration with A2A and MCP AP2 extends existing protocols: - **A2A**: Agent discovers a merchant agent via Agent Card, negotiates purchase via A2A tasks, uses AP2 for the payment step - **MCP**: Agent calls a shopping tool via MCP, the tool uses AP2 internally to process the transaction ## Best Practices - Always require user confirmation (Cart Mandate) before processing payments — agents should never make unauthorized purchases. - Set conservative Intent Mandate limits initially and let users expand them as trust is established. - Use the verifiable credential model for audit trails — every purchase has a cryptographic proof chain. - Implement AP2 as a payment layer on top of A2A or MCP rather than as a standalone protocol. - Handle partial failures gracefully — if payment succeeds but delivery fails, the protocol should support refund flows.