X402 and MPP are both designed for AI agent services, making it convenient for AI agents to purchase services online and automatically pay when calling APIs. Previously, AI agents used paid APIs that required manual payment; Nowadays, it is possible to achieve fully automated, even hundreds or thousands of small and micro payments (such as charging $0.001 per call). Both are using HTTP 402 status code; Both support cryptocurrency and fiat currency (such as credit cards); Both support on chain settlement. If the fiat part is settled through the traditional Stripe channel, it is not entirely on chain settlement. In summary, both X402 and MPP are designed to solve AI agent payment problems. But there are also significant differences: X402 is mainly promoted by Coinbase, with the goal of providing native free payments for encryption. The payment experience is more similar to "cash payment": When the AI agent requests a paid service, the server says "give money", and the AI agent transfers it from its on chain wallet (ERC20, etc.), attaching the transfer proof and making another request. The transaction is completed. Its advantage is that it is very open and free, and everyone can play without being bound to any company or chain, achieving true encryption native decentralization. Its drawback is that, basically, every time a payment is requested, the AI may feel a bit tired when calling frequently (now switching to prepaid mode, not so tired). MPP is mainly promoted by Stripe and Tempo, called Machine Payment Protocol, with the goal of optimizing the payment experience. The payment experience is more similar to "getting a membership card/pre authorization limit": The AI agent first opens a session to authorize the consumption limit in one go. Then, hundreds or thousands of small and micro payments do not need to be transferred each time, just use small vouchers, and finally settle in bulk. The advantages of MPP are that it is very suitable for high-frequency small and micro payment scenarios, as well as Stripe's risk control, tax, and receipt services (visible in the Stripe merchant backend). The shortcomings of MPP are relatively more dependent on the Stripe system+Tempo chain, but it can also be used on any chain, relatively less free and encrypted native than x402. one-sentence summary X402 is more suitable for pure encryption native projects (completely permissionless); MPP is more suitable for players who want to obtain a payment experience similar to traditional finance (such as accessing the Stripe system, tax compliance, risk control, receipts, etc.).