/mpp

name: mpp
description: "Build with MPP (Machine Payments Protocol) - the open protocol for machine-to-machine payments over HTTP 402. Use when developing paid APIs, payment-gated content, AI agent payment flows, MCP tool payments, pay-per-token streaming, or any service using HTTP 402 Payment Required. Covers the mppx TypeScript SDK with Hono/Express/Next.js/Elysia middleware, pympp Python SDK, and mpp Rust SDK. Supports Tempo stablecoins, Stripe cards, Lightning Bitcoin, and custom payment methods. Includes charge (one-time) and session (streaming pay-as-you-go) intents. Make sure to use this skill whenever the user mentions mpp, mppx, machine payments, HTTP 402 payments, Tempo payments, payment channels, pay-per-token, paid API endpoints, or payment-gated services."
metadata:
  version: "0.9.0"
  upstream: "mppx@0.8.15, pympp@0.9.1, mpp@0.11.0, @buildonspark/lightning-mpp-sdk@0.1.4, @stellar/mpp@0.7.1, @solana/mpp@0.7.0, @redotpay/mpp@0.1.2, @defuse-protocol/nearintents-mpp-sdk@0.1.2, mpp-card@0.1.8"
  openclaw:
    homepage: https://github.com/tenequm/skills/tree/main/skills/mpp
    emoji: "💸"
    primaryEnv: MPP_SECRET_KEY
    envVars:
      - name: MNEMONIC
        required: false
        description: BIP-39 mnemonic for client wallet (testnet/regtest only).
      - name: MPP_SECRET_KEY
        required: false
        description: Server-side MPP signing secret (HMAC-binds challenge IDs).
      - name: MPP_REALM
        required: false
        description: Stable realm identifier for mppscan attribution.
      - name: MPPX_RPC_URL
        required: false
        description: Tempo RPC endpoint override for the mppx CLI.
      - name: RPC_URL
        required: false
        description: Generic RPC endpoint override (mppx CLI fallback).
      - name: MPPX_ACCOUNT
        required: false
        description: Default account name for the mppx CLI.
      - name: MPPX_CONFIG
        required: false
        description: Path to the mppx CLI config file.
      - name: STRIPE_SECRET_KEY
        required: false
        description: Stripe API secret key for the Stripe payment method.
      - name: STRIPE_API_KEY
        required: false
        description: Alias for the Stripe API secret key in some examples.
      - name: STRIPE_PROFILE_ID
        required: false
        description: Stripe crypto profile ID for on-chain deposit flows.
      - name: STRIPE_NETWORK_ID
        required: false
        description: Stripe network identifier for SPT settlement.
      - name: PRIVY_APP_ID
        required: false
        description: Privy App ID for Privy server-wallet signers.
      - name: PRIVY_APP_SECRET
        required: false
        description: Privy App Secret for Privy server-wallet signers.
      - name: OPENAI_API_KEY
        required: false
        description: Upstream OpenAI key when gating OpenAI via the payments proxy.
      - name: ANTHROPIC_API_KEY
        required: false
        description: Upstream Anthropic key when gating Anthropic via the payments proxy.

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/).

Tempo token addresses

Public Tempo token addresses referenced throughout this skill. Use the placeholder names in code; full addresses are in the [Tempo documentation](https://docs.tempo.xyz).

| Token | Network | Placeholder | |--------------------|----------|------------------------| | USDC.e (mainnet) | mainnet | `<USDC_TEMPO_MAINNET>` | | pathUSD (testnet) | testnet | `<PATHUSD_TESTNET>` |

When to Use

• Building a **paid API** that charges per request
• Adding a **paywall** to endpoints or content
• Enabling **AI agents** to pay for services autonomously
• **MCP tool calls** that require payment
• **Pay-per-token streaming** (LLM inference, content generation)
• **Session-based metered billing** (pay-as-you-go)
• Accepting **stablecoins** (Tempo), **cards** (Stripe), or **Bitcoin** (Lightning) for API access
• Building a **payments proxy** to gate existing APIs (OpenAI, Anthropic, etc.)

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)

Client                                          Server
  │  (1) GET /resource                            │
  ├──────────────────────────────────────────────>│
  │         (2) 402 + WWW-Authenticate: Payment   │
  │<──────────────────────────────────────────────┤
  │  (3) Sign payment proof                       │
  │  (4) GET /resource + Authorization: Payment   │
  ├──────────────────────────────────────────────>│
  │         (5) Verify + settle                   │
  │         (6) 200 OK + Payment-Receipt          │
  │<──────────────────────────────────────────────┤

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 compatible) | `mppx` (built-in) | Production | | [Lightning](https://mpp.dev/payment-methods/lightning) | Bitcoin over Lightning Network | `@b