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
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
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