mppx

TypeScript SDK for the "Payment" HTTP Authentication Scheme. Full 402 flow: challenge → credential → receipt.

What I can accomplish

• Add 402 payment handling to a client with Fetch.polyfill or Fetch.from.
• Protect HTTP routes with server-side MPP Challenges and Receipt responses.
• Accept one-time Tempo stablecoin payments with tempo.charge.
• Accept metered Tempo stablecoin payments with tempo.session.
• Accept one-time card payments with stripe.charge.
• Verify Credentials directly for custom transports or background workflows.
• Wrap MCP clients and servers so tool calls can require payment.

Required inputs

• Client integrations need a signing account and one or more client payment methods.
• Server integrations need a recipient, currency, amount, and MPP_SECRET_KEY.
• Tempo examples use chain ID 4217 unless a page explicitly covers Moderato testnet.
• Stripe examples need a configured Stripe account and Shared Payment Token flow.
• MCP integrations need the MCP client or server object to wrap.

Constraints

• Keep MPP_SECRET_KEY server-side and out of logs.
• Never commit private keys or wallet seeds.
• Treat runtime 402 Challenges as authoritative for current payment terms.
• Return id and opaque unchanged when responding to a Challenge.
• Use USDC.e for Tempo bridged USDC examples, not generic USDC.

Client

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

// Polyfills globalThis.fetch to handle 402 automatically
Mppx.create({
  methods: [tempo({ account })],
})

const res = await fetch('https://api.example.com/resource')

Without polyfilling:

const mppx = Mppx.create({
  methods: [tempo({ account })],
  polyfill: false,
})

const res = await mppx.fetch('https://api.example.com/resource')

Server

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

const account = privateKeyToAccount('0x...')

const mppx = Mppx.create({
  methods: [
    tempo.charge({ currency: '0x...', recipient: '0x...' }),
    tempo.session({
      account,
      chainId: 4217,
      currency: '0x...',
      store: Store.memory(),
    }),
  ],
  secretKey: process.env.MPP_SECRET_KEY,
})

async function handler(request: Request): Promise<Response> {
  const result = await mppx.charge({ amount: '1.00' })(request)
  if (result.status === 402) return result.challenge
  return result.withReceipt(Response.json({ data: '...' }))
}

Methods

Method	Intent	Description
tempo.charge	charge	One-time stablecoin payment (TIP-20 token transfer on Tempo)
tempo.session	session	Streaming payments via payment channels on Tempo
stripe.charge	charge	One-time payment via Stripe

tempo() returns [tempo.charge, tempo.session] as a tuple using the current v2 Sessions implementation. Use tempo.charge() or tempo.session() individually if you only need one intent. Use tempo.sessionLegacy only for Legacy Sessions v1 compatibility.

Exports

Path	Purpose
mppx	Core primitives (Challenge, Credential, Method, Receipt, PaymentRequest)
mppx/client	Mppx, tempo, stripe, session, Transport
mppx/server	Mppx, tempo, stripe, Transport, Store, NodeListener
mppx/hono	Hono middleware
mppx/express	Express middleware
mppx/nextjs	Next.js middleware
mppx/elysia	Elysia middleware

CLI

mppx includes a CLI for making paid requests during development:

npx mppx account create        # create wallet
npx mppx mpp.dev/api/ping/paid # make paid request
npx mppx example.com -v        # verbose output

References

• TypeScript SDK docs
• Client quickstart
• Server quickstart
• mppx repository
• IETF Specification
• Tempo docs