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Overview

The Machine Payment Protocol (MPP) is a lightweight, Push-based payment standard designed for high-frequency agent interactions. It sits on top of standard W3C HTTP Payment Headers. Unlike x402 (which uses a Pull model where the merchant executes the transfer), MPP operates on a Push model. The agent broadcasts the transfer on-chain, and hands the merchant the transaction hash as proof. The merchant simply verifies the hash exists on-chain and unlocks the resource.

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How mag3nt Handles MPP

Because MPP is a Push protocol, mag3nt acts as a pure payment rail for MPP endpoints, completely removing itself from your agent’s data path. When your agent hits an MPP endpoint, pass the URL to mag3nt: 
// 1. Agent calls an API, gets 402
// 2. Pay via mag3nt
const payment = await mag3nt.payments.paymentsExecute({
  cardId: "sx_...",
  cardToken: "tok_...",
  url: "https://api.example.com/data",
});

// 3. mag3nt broadcasts the transaction and returns the cryptographic receipt
console.log(payment.credential.header_name);  // "Authorization"
console.log(payment.credential.header_value); // "Payment eyJjaGFs..."

// 4. Your agent replays the request with the receipt!
const response = await fetch("https://api.example.com/data", {
  headers: {
    [payment.credential.header_name]: payment.credential.header_value
  }
});
Behind the scenes:
  1. mag3nt parses the WWW-Authenticate: Payment challenge.
  2. mag3nt executes the on-chain transfer to the merchant via CDP.
  3. mag3nt constructs the MPP Authorization: Payment credential containing the transaction hash (type: "hash").
  4. mag3nt hands the credential back to your agent.
This architecture ensures that if your agent is downloading a 5GB file, maintaining a persistent WebSocket, or streaming an LLM response, mag3nt never has to proxy or buffer that data.

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Streaming Micropayments

MPP’s lightweight nature makes it perfect for streaming micropayments (pay-per-token, pay-per-API-call). mag3nt supports continuous payment channels over MPP: 
// Open stream with $5 budget
const stream = await mag3nt.mpp.mppStreamsOpen({
  payerCardId: "sx_payer...",
  payerCardToken: "tok_...",
  receiverCardId: "sx_receiver...",
  budget: 5.0,
});

// Send micro-payments as resources are consumed
await mag3nt.mpp.mppStreamsTick({
  streamId: stream.stream.id,
  amount: 0.001,
  resource: "token-generation",
});

// Check running totals
const status = await mag3nt.mpp.mppStreamsGet(stream.stream.id);
console.log(`Spent: ${status.stream.totalSettled} / ${status.stream.budget}`);

// Close when done
await mag3nt.mpp.mppStreamsClose({ streamId: stream.stream.id });

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Finding MPP Services

You can discover APIs and agents that accept MPP payments by browsing the MPP Services Directory. If you are building a service that accepts MPP, you must throw a 402 Payment Required with a WWW-Authenticate: Payment challenge. To make this frictionless, mag3nt supports Pay Links. You can inject a mag3nt Pay Link directly into your MPP challenge via the settleUrl extension. This allows agents to pay you instantly, while also providing a fallback URL for humans to pay via a web UI.