mpp

# MPP - Machine Payments Protocol MPP is an open protocol (co-authored by Tempo and Stripe) that standardizes HTTP `402 Payment Required` for machine-to-machine payments. Clients pay in the same HTTP request - no accounts, API keys, or checkout flows needed. The core protocol spec is submitted to the IETF as the [Payment HTTP Authentication Scheme](https://datatracker.ietf.org/doc/draft-ryan-httpauth-payment/). Code in this skill uses placeholder token names (`<USDC_TEMPO_MAINNET>`, `<PATHUSD_TESTNET>`); the real addresses live in the [Tempo documentation](https://docs.tempo.xyz) and `references/tempo-method.md`. ## Core Architecture Three primitives power every MPP payment: 1. **Challenge** - server-issued payment requirement (in `WWW-Authenticate: Payment` header) 2. **Credential** - client-submitted payment proof (in `Authorization: Payment` header) 3. **Receipt** - server confirmation of successful payment (in `Payment-Receipt` header) ## Payment Methods & Intents MPP is payment-method agnostic. Each method defines its own settlement rail: | Method | Rail | SDK Package | Status | |--------|------|-------------|--------| | [Tempo](https://mpp.dev/payment-methods/tempo) | TIP-20 stablecoins on Tempo chain | `mppx` (built-in) | Production | | [Stripe](https://mpp.dev/payment-methods/stripe) | Cards/wallets (SPT) + on-chain crypto deposit | `mppx` (built-in) | Production | | [EVM](https://mpp.dev/payment-methods/evm) | EIP-3009 stablecoin authorizations (x402-exact c...