402-mcp

L402 + x402 client MCP that gives AI agents economic agency. Discover, pay for, and consume any payment-gated API — no human registration, no API keys, no middlemen.

• Discover paid APIs on Nostr — no URLs needed upfront
• Auto-pay with Lightning (NWC), Cashu ecash, or human QR fallback
• Credentials cached and encrypted at rest (AES-256-GCM)
• Works with any L402 server — toll-booth, Aperture, or any future implementation

Quick start

1. Install

npx 402-mcp

2. Connect to Claude Code

claude mcp add 402-mcp -- npx 402-mcp

3. Try it

Ask Claude: "Search for paid joke APIs using l402_search" — no wallet needed, just discovery.

Ready to make paid calls? See the full quickstart guide to set up a wallet and watch your agent pay for its first API call.

How it works

graph LR
    A["1. l402_config()"] --> B["2. l402_discover(url)"]
    B --> C["3. Agent reasons<br/>about pricing"]
    C --> D["4. l402_buy_credits()<br/>or l402_fetch()"]
    D --> E["5. l402_fetch(url)<br/>with credentials"]
    E --> F["6. Data returned<br/>+ balance cached"]

Example session:

Agent: "I need routing data from routing.trotters.cc"

1. l402_config()
   -> nwcConfigured: true, maxAutoPaySats: 1000

2. l402_discover("https://routing.trotters.cc/api/route")
   -> 10 sats/request, toll-booth detected, tiers available

3. Agent reasons: "I need ~20 requests. The 500-sat tier
   gives 555 credits. Better value."

4. l402_buy_credits(url, amountSats=500)
   -> Paid 500 sats, received 555 credits

5. l402_fetch("https://routing.trotters.cc/api/route?from=...&to=...")
   -> 200 OK, route data, 545 credits remaining

For detailed architecture and payment flow diagrams, see docs/architecture.md.

Configuration

| Variable | Default | Description | |----------|---------|-------------| | NWC_URI | - | Nostr Wallet Connect URI for autonomous Lightning payments | | CASHU_TOKENS | - | Path to Cashu token store file | | MAX_AUTO_PAY_SATS | 1000 | Safety cap; payments above this require human confirmation | | CREDENTIAL_STORE | ~/.402-mcp/credentials.json | Persistent macaroon/credential storage | | TRANSPORT | stdio | Transport mode: stdio or http | | PORT | 3402 | HTTP server port (when TRANSPORT=http) | | TRANSPORT_PREFERENCE | clearnet | Preferred network transport: clearnet, tor, or hns | | TOR_PROXY | - | SOCKS5 proxy for .onion addresses (e.g. socks5h://127.0.0.1:9050) | | SOCKS_PROXY | - | Generic SOCKS5 proxy for all requests when set | | HNS_GATEWAY_URL | - | HTTP gateway for Handshake (.hns) domains (e.g. https://hns.to) |

Transport selection and fallback

When a kind 31402 event advertises multiple URLs (one per transport), 402-mcp selects the best one based on your configuration:

1. Preference first — if TRANSPORT_PREFERENCE=tor and a .onion URL is available, it is tried first.
2. Availability fallback — if the preferred transport is unreachable (proxy not configured, timeout), the client falls back to the next URL in the list.
3. Clearnet default — if no preference is set, clearnet URLs are tried before .onion or HNS entries.

Services can announce multiple endpoints for the same service (same pricing, same macaroon key) on different transports. This is purely for censorship resistance; you do not need to re-authenticate when switching transports. To reach Tor or HNS endpoints you must configure the corresponding proxy/gateway env vars above.

Tools

Core L402 (any server)

| Tool | Description | |------|-------------| | l402_config | Introspect payment capabilities (wallets, limits, credential count) | | l402_discover | Probe an endpoint to discover pricing without paying | | l402_fetch | HTTP request with L402 support; auto-pays if within budget | | l402_pay | Pay a specific invoice (NWC, Cashu, or human-in-the-loop) | | l402_credentials | List stored credentials and cached balances | | l402_balance | Check cached credit balance for a server | | l402_search | Discover L402 services on Nostr relays (kind 31402 announcements) | | l402_store_token | Store an L402 token obtained from a payment page |

toll-booth extensions

| Tool | Description | |------|-------------| | l402_buy_credits | Browse and purchase volume discount tiers | | l402_redeem_cashu | Redeem Cashu tokens directly (avoids Lightning round-trip) |

Payment methods

Three payment rails, tried in priority order:

1. NWC (Nostr Wallet Connect) — fully autonomous; pays from your connected wallet
2. Cashu — fully autonomous; melts ecash tokens to pay invoices
3. Human-in-the-loop — presents QR code, polls for settlement

The agent can override the method per-call, or you can configure only the methods you want.

Safety

MAX_AUTO_PAY_SATS caps any single autonomous payment. Above this limit, the agent must ask the human for approval. The agent can read this limit via l402_config and factor it into purchasing decisions.

Privacy

402-mcp stores credentials locally on your machine only (~/.402-mcp/credentials.json, encrypted at rest). No data is sent to any third party. No accounts, no tracking, no analytics. Payments use Lightning or Cashu — pseudonymous by design.

Ecosystem

Browse live L402 services at 402.pub — the decentralised marketplace for payment-gated APIs.

| Project | Role | |---------|------| | toll-booth | Payment-rail agnostic HTTP 402 middleware | | satgate | Pay-per-token AI inference proxy (built on toll-booth) | | 402-mcp | MCP client — AI agents discover, pay, and consume L402 + x402 APIs | | 402-announce | Publish L402 services on Nostr for decentralised discovery |

402-mcp is the payment-rail agnostic alternative to Lightning Labs' lightning-agent-tools and Coinbase's x402 — no Lightning node required, multiple wallets, encrypted credentials.

| | 402-mcp | Lightning Labs agent tools | |---|---|---| | Payment rails | NWC + Cashu + human fallback | Lightning only | | Node required? | No — connects to any NWC wallet | Yes — runs LND | | Server compatibility | Any L402 server | Aperture-focused | | Spend safety | Per-payment cap + rolling 60s window | Per-call max-cost | | Credential storage | Encrypted at rest (AES-256-GCM) | File permissions | | Privacy | No PII, SSRF protection, error sanitisation | Standard |

Use Lightning Labs' tools if you want agents that run their own Lightning node. Use 402-mcp if you want agents that pay from any wallet without infrastructure.

See CONTRIBUTING.md for development setup and guidelines.

Built by @forgesworn.

• Lightning tips: [email protected]
• Nostr: npub1mgvlrnf5hm9yf0n5mf9nqmvarhvxkc6remu5ec3vf8r0txqkuk7su0e7q2

Licence

MIT