Documentation

MPP Gate is a payment control layer for autonomous AI agents, built on the Machine Payments Protocol (MPP).

It sits between your agents and the payment rail — giving you per-agent budgets, spend limits, auto-stop, and a full audit trail of every payment an agent makes.

MPP Gate also acts as a fee payer, co-signing transactions so your agents never need to hold gas tokens — just stablecoins like USDC.

Integrate MPP Gate in two steps:

import { Mppx, tempo } from 'mppx/express'

const mppx = Mppx.create({
  secretKey: process.env.MPP_SECRET_KEY,
  methods: [tempo({
    currency: '0x20c000000000000000000000b9537d11c60e8b50',
    recipient: '0xYourAddress',
    feePayerUrl: 'https://facilitator.mppgate.com',
  })],
})

import { Mppx, tempo } from 'mppx/client'
import { privateKeyToAccount } from 'viem/accounts'

const client = Mppx.create({
  methods: [tempo({
    account: privateKeyToAccount(process.env.AGENT_KEY),
  })],
})

// Paid fetch — handles 402 → pay → retry automatically
const res = await client.fetch('https://api.example.com/endpoint', {
  method: 'POST',
  body: JSON.stringify({ query: 'hello' }),
})

The MPP payment flow with MPP Gate as the control layer:

1. Agent requests an MPP-gated API endpoint.
2. Server responds 402 with a WWW-Authenticate header containing the payment challenge (amount, currency, recipient).
3. Agent signs a token transfer transaction but does not broadcast it.
4. MPP Gate checks budget, co-signs as fee payer, broadcasts the transaction, and logs it to the audit trail.
5. Agent retries the original request with payment credentials.
6. Server verifies the payment on-chain and serves the response.

MPP supports two payment modes:

MPP Gate is essential for pull mode — the mode most AI agents use. Without it, every agent would need to hold gas tokens on every chain.

• MPP Protocol Specification
• MPP Developer Docs
• Solana MPP SDK
• Tempo Documentation
• MPP Gate on GitHub