x402 Endpoint Inspector
An x402 endpoint inspector reads the HTTP 402 payment challenge an API returns and validates the payment document (accepts[] entries, discovery manifests, required shapes) without paying, signing, or settling anything. A malformed challenge is how an integrator discovers a broken billing flow only after wiring in a wallet; catching it preflight is the point. mcpreflight inspect prints exactly which step of the challenge diverges from the spec, plus latency, size, and a response digest, all read-only. The command below reproduces any single result.
Read the full guide in the source repository.
npx @eidonze/mcpreflight@0.1.5 inspect https://your-api.example/paid --method=POST --json
Checks HTTP 402, payment documents, v1/v2 accepts[], discovery manifests, latency, size, and response digest. It never pays, signs, settles, or retries.
Weekly cohort tracking
Cohort: registry endpoints whose title, description, or URL mentions x402 or HTTP-402 (definition fixed 2026-10-15, matching finding 6). Snapshotted every Monday by the rescan workflow. passRate is the clean anonymous handshake share; unknown endpoints gave no anonymous response, and the auth-gated column tracks how many of those are confirmed intentional gates.
| date | cohort | pass | passRate | auth-gated | unknown | fail |
|---|---|---|---|---|---|---|
| 2026-10-15 | 293 | 218 | 74.4% | 0 | 74 | 1 |
Preflight any single endpoint yourself, read-only: npx @eidonze/mcpreflight inspect <url> for the 402 challenge, npx @eidonze/mcpreflight schema <url> for the MCP handshake. Open source, MIT.