x402 Doctor

Endpoints (5 live)

• GET /api/v1/preflight/batch — Are these x402 endpoints safe to pay? Up to 10 endpoints in one call (?url=a&url=b): per endpoint go / caution / no_go, the recommended payment option and why, plus totals. For marketplaces and agents that weigh several services. Never pays the endpoints. (0.005 USDC on Solana)
• GET /api/v1/diagnose — Why is my x402 endpoint broken? Diagnose and debug an x402 payment endpoint (or MCP server) when payments fail: checks the 402 challenge, accepts[] (network, payTo, amount, asset), resource URL, Solana settlement readiness, which wallets and agents can pay, Bazaar/OpenAPI discovery and the browser paywall. Returns every check with a fix hint. Read-only: never pays. (0.01 USDC on Solana)
• GET /api/v1/preflight/deep — Should my agent pay this expensive x402 endpoint? The pre-payment verdict plus the full diagnosis, the 30-day history per day, how reliable the seller's other endpoints are and whether the endpoint moved domains. Never pays the endpoint. (0.01 USDC on Base)
• GET /api/v1/fix — How do I fix my broken x402 endpoint? Diagnoses it, then returns per problem the concrete change as code for your stack (Express, Next.js, Hono or raw HTTP), filled in with your own payTo, amount, network and route. (0.05 USDC on Base)
• GET /api/v1/preflight — Is this x402 endpoint safe to pay? Check it before your AI agent pays: go / caution / no_go, the recommended payment option, and why (payment would fail, over your budget, price above advertised, not HTTPS, unknown token). Never pays the endpoint. Cached 10 min. (0.001 USDC on Base)

MCP tools (8)

x402-doctor https://x402-doctor.fizzl.eu/mcp

• check_payment_proof — Free: after paying an x402 endpoint, pass the PAYMENT-RESPONSE header it returned (X-PAYMENT-RESPONSE in v1). Returns the transaction, network and payer it names, whether that transaction exists on-chain and succeeded, and which USDC moved from whom to whom, with an explorer link. Read-only. Limited to 10 calls per hour.
• feedback — Report a bug, a missing feature or anything else about this service, in a structured way. Free. A person reads every report; nothing is run or changed automatically.
• x402_diagnose — Paid ($0.01 USDC via x402 on Base or Solana): diagnose an x402 endpoint the way a paying agent would, without paying it: the 402 challenge format, every accepts[] option, the resource URL, Solana settlement readiness, which wallets can pay, Bazaar/OpenAPI discovery and the browser paywall. Returns every check with pass/warn/fail and a fix hint. Same as GET /api/v1/diagnose. The answer carries a signed receipt (EIP-191, bound to your arguments) that proves later which verdict you got.
• x402_fix — Paid ($0.05 USDC via x402 on Base or Solana): diagnoses your x402 endpoint, then returns per problem the concrete change as code for your stack (express, next, hono, node, python, generic), filled in with your own payTo, amount, network and route. Same as GET /api/v1/fix. The answer carries a signed receipt (EIP-191, bound to your arguments) that proves later which verdict you got.
• x402_preflight — Paid ($0.001 USDC via x402 on Base or Solana): call this before your agent pays an x402 endpoint. Returns go, caution or no_go, the recommended payment option, and why: payment would fail, over your budget (max_usd), price above what is advertised, not HTTPS, unknown token, its 30-day track record. Never pays the endpoint. Same as GET /api/v1/preflight. The answer carries a signed receipt (EIP-191, bound to your arguments) that proves later which verdict you got.
• x402_preflight_batch — Paid ($0.005 USDC via x402 on Base or Solana): the pre-payment check for up to 10 x402 endpoints at once. Per endpoint go, caution or no_go, the recommended payment option and why, plus totals. For marketplaces and agents that weigh several services. Never pays the endpoints. Same as GET /api/v1/preflight/batch. The answer carries a signed receipt (EIP-191, bound to your arguments) that proves later which verdict you got.
• x402_preflight_deep — Paid ($0.01 USDC via x402 on Base or Solana): for expensive calls. The pre-payment verdict (go, caution or no_go) plus the full diagnosis, the 30-day history per day, how reliable the seller's other endpoints are and whether the endpoint moved domains. Never pays the endpoint. Same as GET /api/v1/preflight/deep. The answer carries a signed receipt (EIP-191, bound to your arguments) that proves later which verdict you got.
• x402_quick_check — Free: does this x402 endpoint work for a paying agent? Returns pass, warn or fail with the number of problems and the top three. Limited to 10 calls per hour. For every check use x402_diagnose ($0.01); for code changes x402_fix ($0.05); before paying someone else's endpoint x402_preflight ($0.001).