Purpose x402-discovery-mcp solves the "discovery" problem in the x402 ecosystem. x402 is an HTTP-native micropayment standard proposed by Coinbase: after an AI agent accesses an endpoint, it receives an HTTP 402 challenge, pays with USDC on Base, and obtains the data, without API keys or subscriptions. The official directory only lists service names and lacks availability, latency, facilitator compatibility, and trust signals, so this MCP server connects agents to the x402 Service Discovery API and provides a continuously updated directory with real-time quality signals.
Main capabilities
- Discovery: find x402 services by capability, category, and price ceiling.
- Quality signals: uptime percentage, latency (milliseconds), facilitator compatibility, ERC-8004 trust score.
- Registration: register new x402 endpoints through the API or MCP tools.
- Execution: scout_relay completes discovery, x402 payment, and retry on failure in a single call and returns the result; it is an autonomous payment router.
- MCP tools: 9 in total, including 5 discovery tools and 4 relay tools.
- Other components: Python SDK, terminal CLI (x402scout), ScoutGate (wraps an existing API as x402 payment in 2 minutes, with no protocol knowledge required, automatically listed in x402Scout, and settled in USDC on Base mainnet).
How to use Multiple access methods are supported:
- Docker (recommended): add to claude_desktop_config.json, Cursor MCP settings, or Windsurf configuration.
- npx (no Docker required).
- Direct API: the Discovery API is publicly accessible and requires no authentication.
- CLI: x402scout can search the complete x402 service directory in the terminal; see cli/README.md for usage. Payment is completed through the x402 HTTP protocol using an EIP-712 signed TransferWithAuthorization, rather than a direct ERC-20 transfer; the signature is verified by the server, and settlement on-chain is done through receiveWithAuthorization.
SuitUse cases
- Find, evaluate, and call payable x402 services within MCP clients such as Claude, Cursor, and Windsurf.
- Agent workflows that need to select services by quality and trust score and check facilitator compatibility.
- Providers that want to quickly bring an existing API into x402 payment and charge per call.
- Scenarios that require autonomous payment routing, automatic retries, and auditing.
Fees and limits
- x402_discover calls cost $0.010 USDC, paid through the x402 protocol of its own service.
- scout_relay charges max($0.003, 2.5% of the downstream transaction amount) per routed call.
- ScoutGate charges 2% per transaction (minimum $0.002).
- Location bidding: providers can register routing priority bids, with a $0.01 registration fee, x402-gated; bids are used only as a tiebreaker after trust score filtering, always "quality first."
- The project is built on the Coinbase x402 protocol, Base network, ERC-8004, and Model Context Protocol.
- Detailed information about the specific interfaces of the Python SDK, the complete list of MCP tools, and the parameters of each tool is not provided in the materials.
