Question 1

What is the Machine Payments Protocol (MPP)?

Accepted Answer

MPP is an open protocol that lets software (AI agents, scripts, or any automated client) pay for internet services. It standardizes HTTP 402 "Payment Required" status code into a working payment layer.

Question 2

What is the difference between MPP and x402?

Accepted Answer

x402 is a crypto-native payment protocol. MPP is a broader payment abstraction that works across crypto, fiat, and custom rails through one interface. Beyond that, MPP removes x402's required facilitator middleware and has a native session model for high-frequency micropayments.

Question 3

How does MPP handle a payment?

Accepted Answer

The entire process happens inside a single HTTP request cycle. Five steps: (1) the agent sends a request, (2) server returns HTTP 402 with price and accepted methods, (3) agent's wallet signs a payment credential, (4) agent retries with that credential as an HTTP header, (5) server verifies, settles, and delivers the resource plus a receipt.

Question 4

What are MPP sessions and why do they matter for AI agents?

Accepted Answer

MPP sessions let agents make repeated payments efficiently without settling on-chain every time. Instead, an agent pre-funds a balance and sends lightweight signed vouchers for each request, which are settled later in one transaction. This makes high-frequency use cases like LLM token billing and streaming APIs efficient.

Question 5

What’s the difference between MCP and MPP?

Accepted Answer

MCP (Model Context Protocol) gave agents a standard way to talk to tools. MPP (Machine Payments Protocol) gives them a standard way to pay for those tools. They're complementary layers of the same stack. MCP handles communication; MPP handles payment. MPP is explicitly designed to work over MCP alongside standard HTTP and JSON-RPC.

What is a Machine Payments Protocol (MPP)? How AI Agents Learning to Pay