x402 vs MPP
x402 is a per-request payment rail built on HTTP 402. MPP is a broader machine payments protocol for agents paying agents. They solve overlapping problems at different layers.
The short answer
Use x402 to charge agents per API request or MCP tool call today — it's the mature, widely-adopted rail. Reach for MPP when you're building autonomous agents that settle with each other across multi-step tasks. They're complementary: MPP can use x402 as its settlement step.
Side-by-side
When to choose which
Choose x402
Charge per HTTP request / MCP call, USDC pricing, EVM/Solana stack. Start with the SDK or browse x402 projects.
Choose MPP
Autonomous agent-to-agent settlement across tasks. Browse MPP projects or the MPP overview.
Use both
Layer them — MPP coordinates the agent interaction, x402 settles the individual payment.
Frequently asked questions
What is the difference between x402 and MPP?
x402 is a specific scheme for paying for one HTTP resource: a server returns HTTP 402 with payment terms and the client pays USDC on-chain. MPP (Machine Payments Protocol) is a broader standard for autonomous agent-to-agent and machine-to-machine payments. In short, x402 is a focused per-request payment rail, while MPP is a wider settlement protocol that can even use x402 underneath.
Is x402 or MPP better for AI agents?
For charging agents per API request or per MCP tool call today, x402 is the more mature, widely-implemented choice. For building autonomous agents that pay each other for multi-step tasks, MPP targets that broader coordination problem. They are complementary rather than mutually exclusive — MPP can settle via an x402 payment.
Can x402 and MPP work together?
Yes. They operate at different layers. An MPP-based agent-to-agent flow can use x402 as its concrete payment/settlement step, since x402 provides a clean, standardized way to charge for an HTTP resource in USDC.
How many x402 and MPP projects are there?
We currently track 1.2k x402 projects and 142 MPP projects in the ecosystem directory, ranked by GitHub stars. Browse the full lists on our x402 projects and MPP projects pages.
See also: all agent payment protocols · x402 vs AP2 · x402 vs L402 · full comparison