A comparison of five emerging agent payment protocols (APPs) that enable AI agents to autonomously execute financial transactions via APIs. AP2 (Google) uses cryptographically-signed mandates to enforce user intent. ACP (OpenAI + Stripe) provides RESTful checkout endpoints with time-bound payment tokens, suited for human-present commerce. x402 (Coinbase) leverages HTTP 402 for instant crypto-only payments with no account required. Stripe MPP extends the 402 pattern to support both traditional and crypto payments with upfront deposit vouchers. AGTP introduces agent-specific HTTP verbs including a PURCHASE command and a trust index, though it relies on external payment tools rather than being a native payment protocol. Each protocol involves different trade-offs in autonomy, payment method support, and security.
Table of contents
1. Agents Payment Protocol (AP2)2. Agentic Commerce Protocol (ACP)3. x4024. Stripe MPP5. Agent Transfer Protocol (AGTP)Agent Payment Protocols: When to Use EachAI SummarySort: