What is the Machine Payments Protocol (MPP)?

Who created MPP?

Stripe and Tempo co-authored MPP and announced it on March 18, 2026. Tempo is a payments blockchain developed with funding from Stripe and Paradigm, and its mainnet went live the same day.

The spec is written up as an IETF Internet-Draft titled "The Payment HTTP Authentication Scheme", with authors from Tempo Labs and Stripe. As of September 2026 it is an individual draft at version 01. No IETF working group has adopted it.

How does an MPP payment work?

MPP uses a challenge, a credential, and a receipt, carried in standard HTTP authentication headers. The client asks, the server challenges with a price, the client pays and retries, and the server answers with a receipt.

• 1. The client requests a paid resource.
• 2. The server returns HTTP 402 with a WWW-Authenticate header using the Payment scheme. It names the method, the intent, and the amount.
• 3. The client pays with the named method and retries with an Authorization header carrying the credential.
• 4. The server verifies the payment, returns the resource, and adds a Payment-Receipt header.

Which payment methods does MPP support?

MPP separates the protocol from the payment method. The mpp.dev site lists Tempo, other EVM chains, Solana, Stellar, Lightning, and Stripe cards, among others. Custom methods are allowed. It names Tempo and Stripe as the methods in production.

Through Stripe, a business can take MPP payments as USDC.e on Tempo, USDC on Solana, or cards and buy now pay later through Shared Payment Tokens. Stripe lists minimums of 0.01 USDC for stablecoins and 0.50 USD for card payments.

What are MPP intents and sessions?

An intent says what kind of payment the server wants. MPP defines charge for a one-time payment, session for ongoing or metered use, and subscription for recurring payments.

Sessions support streaming and metered billing. That fits LLM tokens or data streams, where the cost builds up over time.

How is MPP different from x402?

Both protocols put a price in a 402 response and let the client pay and retry. They differ in headers, payment rails, and who runs them. x402 is stablecoin-first and settles through facilitators. MPP is method-agnostic and uses HTTP authentication headers.

Can a server support both MPP and x402?

Yes. The mpp.dev site says MPP can coexist with x402, and Stripe accepts both. The two use different headers, so a server can offer each without conflict.

Locus does this. It runs separate x402 and MPP hosts for the same managed APIs, so a buyer can pay with whichever protocol its client supports.

Where do I find MPP services?

The mpp.dev services directory lists MPP endpoints, with a public catalog API and a services MCP server for agents. On September 29, 2026, its API listed 142 services, and 43 of them were hosted by Locus.

How does Locus use MPP?

Locus runs MPP endpoints for its managed APIs, one host per provider in the form namespace.mpp.paywithlocus.com. Payment is USDC.e on Tempo. Examples in the mpp.dev directory include Alpha Vantage, Apollo, Brave Search, Perplexity, and Tavily.

Locus Pro also pays third-party MPP services for your agent from one prepaid credit balance. These are priced live per call. Pass max_charge_credits as a ceiling, and Locus declines before dispatch if the price is higher.

What are the limits of MPP?

MPP is new, and parts of it are still in preview. Check these before you build on it.

• The IETF draft is an individual submission, not an adopted standard.
• Tempo payments use USDC.e on the Tempo chain, not USDC on Base. You need funds on the right chain.
• Stripe card payments have a 0.50 USD minimum, which rules out sub-cent card calls.
• Stripe stablecoin payments are not available to businesses in New York.
• Gasless Tempo payments through Stripe are in private preview.
• The protocol sets no budget for the payer. Spending limits live in the wallet or platform that pays.