What is the Machine Payments Protocol?

MPP is an open standard for machine-to-machine payments over HTTP 402, co-authored by Stripe and Tempo and launched in March 2026. Servers issue payment challenges, clients pay with a supported method such as stablecoins or cards, and retry with proof of payment to receive the resource.

Is MPP the same as x402?

No, but they are closely related. Both use HTTP 402 to request payment. x402, from Coinbase, centres on stablecoin payments such as USDC on Base. MPP supports multiple payment methods, including cards and Tempo stablecoins, and shares signature primitives with x402, so one endpoint can serve both.

What payment methods does MPP support?

MPP is payment-method agnostic. Documented methods include stablecoins on Tempo, cards through Stripe Shared Payment Tokens, Bitcoin Lightning, Solana, and other chains. Each method has its own specification maintained by the relevant rail, and servers advertise which methods they accept for each resource.

Machine Payments Protocol (MPP) Explained

The Machine Payments Protocol (MPP) is an open standard for machine-to-machine payments over HTTP 402, co-authored by Stripe and Tempo and launched on March 18, 2026. A server answers with a payment challenge, the client pays with a supported method such as stablecoins or a card token, and retries with proof.

Where MPP came from

Stripe and Tempo published MPP on March 18, 2026, the same day Tempo's payments-focused blockchain reached mainnet. Stripe describes it as an open standard for machine-to-machine payments via HTTP 402. The core specification is published as an IETF Internet-Draft for a Payment HTTP authentication scheme, an individual submission that the draft itself notes has no formal standing at the IETF.

The basic flow

A client, often an AI agent, requests a paid resource. The server responds with HTTP 402 and a payment challenge describing what it accepts. The client selects a method, completes payment, and retries the request with a credential proving payment. The server verifies the credential and returns the resource. The pattern mirrors HTTP authentication, with payment as the proof.

Payment-method agnostic

Unlike protocols centred on a single asset or chain, MPP lets each server advertise multiple payment methods. Documented methods include stablecoins on Tempo, cards through Stripe's Shared Payment Tokens, Bitcoin Lightning, Solana, and other chains. Each payment method specification is maintained by its own rail, while the core protocol stays neutral.

Sessions for tiny charges

Paying onchain for every sub-cent request would cost more in overhead than the charge itself. MPP defines sessions that let a client and server account for many small charges and settle them efficiently. Sessions make per-token, per-byte, or per-second pricing practical for APIs and compute services.

Relationship to x402

x402, created by Coinbase, also uses HTTP 402 to request payment, typically in stablecoins such as USDC on Base. MPP and x402 share the same signature primitives, EIP-3009 and Permit2, which is what makes serving both from one endpoint practical: a provider can keep an x402 server or use MPP tooling to answer both kinds of client.

Stripe support

Stripe's machine payments documentation lists MPP support with stablecoins on Tempo and Solana, and x402 support with USDC on Base. Merchants using Stripe can accept machine payments and see them alongside other Stripe activity, with settlement handled through Stripe.

Cards in a machine protocol

Including cards lets services charge agents whose principals prefer card billing. Shared Payment Tokens scope a card credential to a seller, amount, and time, so the agent never holds raw card details. Card payments carry minimum amounts and different settlement timing from stablecoins.

Who MPP is for

MPP targets API providers, data sellers, compute platforms, and other services that want to charge software clients without signups, and agent builders who want one way to pay many services. It suits teams that want to accept several payment rails through one protocol.

How it compares with other protocols

MPP and x402 operate at the HTTP payment layer. The Agentic Commerce Protocol and Google's Universal Commerce Protocol handle shopping and checkout between agents and merchants. Google's Agent Payments Protocol focuses on mandates proving user authorisation. These layers can be combined in one system.

Implementation

Providers integrate MPP through libraries and Stripe's machine payments features, declaring prices and accepted methods for each endpoint. Clients use SDKs that detect 402 challenges, pick a method, pay, and retry automatically. Testing on test networks and Stripe test mode avoids real charges during development.

Safety for agent payers

MPP standardises how payment is requested and proven, not how much an agent may spend. Agent builders still need bounded wallets or scoped credentials, per-request price checks, spending caps, and logs, so a misbehaving agent cannot drain funds through valid-looking challenges.

Who governs Machine Payments Protocol (MPP) Explained

The MPP site describes the protocol's governance, with the core specification separate from per-method specifications maintained by each payment rail. Because the IETF draft is an individual submission, the specification may change before any formal standardisation.

Choosing between MPP and x402

If you want stablecoin pay-per-call on Base with a wide existing ecosystem, x402 is a direct fit. If you want to accept several rails, including cards and Tempo stablecoins, through one protocol, MPP is designed for that. Because the two share signature primitives, supporting both is practical.

An example request

An agent calls a search API that charges a fraction of a cent per query. The first request returns HTTP 402 with a challenge listing accepted methods. The agent's client library opens a session, authorises a spending limit for that session, and sends subsequent queries with session credentials. The provider accounts for each query and settles the session total efficiently rather than settling every query separately.

What MPP does not cover

MPP does not define product catalogs, shopping carts, returns, or merchant-of-record arrangements; those belong to commerce protocols such as ACP or UCP. It also does not prove the identity of the human behind an agent, which identity protocols address. Its scope is requesting and proving payment for machine-consumed resources.

Frequently asked questions

What is the Machine Payments Protocol?: MPP is an open standard for machine-to-machine payments over HTTP 402, co-authored by Stripe and Tempo and launched in March 2026. Servers issue payment challenges, clients pay with a supported method such as stablecoins or cards, and retry with proof of payment to receive the resource.
Is MPP the same as x402?: No, but they are closely related. Both use HTTP 402 to request payment. x402, from Coinbase, centres on stablecoin payments such as USDC on Base. MPP supports multiple payment methods, including cards and Tempo stablecoins, and shares signature primitives with x402, so one endpoint can serve both.
What payment methods does MPP support?: MPP is payment-method agnostic. Documented methods include stablecoins on Tempo, cards through Stripe Shared Payment Tokens, Bitcoin Lightning, Solana, and other chains. Each method has its own specification maintained by the relevant rail, and servers advertise which methods they accept for each resource.