MPP — Machine Payments Protocol

What is MPP?

MPP (Machine Payments Protocol) is an open machine-to-machine payment protocol from Stripe and Tempo Labs, launched in March 2026. It formalizes HTTP 402 for agent payments: stablecoins and cards are accepted within a single HTTP request, and a session primitive handles streaming transactions.

Why do you need MPP?

As the AI economy grows, agents increasingly buy services from other agents or external services. MPP creates a common language for such transactions, with several key differences from x402:

	x402	MPP
Author	Coinbase	Stripe + Tempo Labs
Payment methods	Stablecoins (USDC)	Stablecoins + cards
Sessions	No	Session primitive for streaming
Service directory	No	100+ services

MPP targets a broader market: alongside stablecoins, traditional payment instruments are supported, lowering the barrier to entry.

How do you implement MPP?

Declare MPP support in ai-agent.json:

{
  "payments": {
    "mpp": "https://api.example.com/mpp"
  }
}

Or via a Link header:

Link: <https://api.example.com/mpp>; rel="mpp-endpoint"

Full integration requires implementing an MPP endpoint according to the specification at mpp.dev. The session primitive is used for streaming services where a transaction spans over time (subscriptions, long-running tasks).

How do we check MPP?

The MPP check in the scanner is informational (does not affect the main score). The scanner checks for protocol declaration in two ways:

1. GET /.well-known/ai-agent.json → payments.mpp field
2. HEAD / → Link header with rel="mpp-endpoint"

Actual payment processing is not tested. If a declaration is found → pass, if absent → fail.