x402fix: x402 endpoint doctor

Point x402fix at any paid x402 URL and it tells you, in order of severity, what will break payments or keep the route out of the Bazaar / x402scan, and how to fix each problem. It probes the route without paying: GET, HEAD, an empty POST, POST {} and a CORS preflight. Then it grades the route A to F.

• Transport: 402 on GET, HEAD and empty POST; CORS preflight; Access-Control-Expose-Headers: PAYMENT-REQUIRED; cacheable 402s; redirects; auth walls; latency.
• x402 v2: PAYMENT-REQUIRED header; resource.url; CAIP-2 networks; amount given as a string of atomic units; canonical USDC asset; the EIP-712 domain (extra.name and extra.version) for each chain; payTo format; Solana extra.feePayer; maxTimeoutSeconds.
• x402 v1: JSON body; maxAmountRequired; network names; whether v1 and v2 terms agree.
• Bazaar: extensions.bazaar info and schema. It validates info against schema (JSON Schema 2020-12), flags external $ref and old drafts, and checks method and input/output consistency.
• Multichain: price drift across networks, duplicate entries, networks the CDP facilitator doesn't settle, and which of Base, Polygon, Arbitrum One and Solana you accept.
• Check tier extras: the CDP facilitator's own validate verdict and Bazaar index status, payee checks (EVM contract vs wallet, whether the Solana USDC token account exists, CounterpartyCheck screening), drift between /openapi.json and /.well-known/x402, a generated, self-validated extensions.bazaar block, and a multichain accepts snippet for Hono, Express or Next.

Live API: https://api.youraitools.co/x402fix (origin: https://x402fix.agentgate.workers.dev)

| Route | Price (USDC) | Returns | |---|---|---| | GET /v1/preview?url= | free, 10/min | grade, score, status, counts, detected versions and networks | | GET|POST /v1/lite?url= | $0.005 | every check plus a numbered fix list | | GET|POST /v1/check?url=&framework=hono | $0.02 | lite + CDP verdict, payee checks, docs drift, generated Bazaar block and accepts | | GET|POST /v1/site?url=https://origin | $0.05 | finds up to 8 paid routes from /.well-known/x402 and /openapi.json, grades each, checks doc drift |

Payment: x402 v2 or v1, exact USDC on Base, Polygon, Arbitrum One or Solana. Prepaid credits (Authorization: Bearer) are also accepted, via https://api.youraitools.co/credits.

MCP

• Remote: https://api.youraitools.co/x402fix/mcp (tool check_x402_endpoint, free preview)
• stdio: npx -y @agentgate-builder/x402fix. Set X402FIX_X402_PRIVATE_KEY to a Base wallet key holding a little USDC, and it pays for check reports ($0.02 each).
• Docker: docker build -t x402fix-mcp . && docker run -i --rm x402fix-mcp

CI

curl -s "https://api.youraitools.co/x402fix/v1/preview?url=https://your.api/v1/paid" | jq -e '.status != "broken"'

Notes

• Probes are unpaid and never send payment headers. Private, loopback and link-local hosts are refused, and ports are limited to 80, 443, 8080, 8443, 3000, 8000 and 8787.
• Fixes are suggestions. A passing grade does not guarantee listing or settlement.

Develop: npm test; npm start (Node, port 8795); npx wrangler deploy. MIT.