Your x402 payment failed and the only feedback was a bare 402? Paste the broken payload — the clinic tells you exactly what is wrong and how to fix it. Free. No payment, no signup.
POST https://api.mekongtradeintel.com/clinic/diagnose
Content-Type: application/json
{ "payload": <object | base64 string>, "endpoint": "tokenprice" }
Response: { ok, class, explanation, fix_steps, corrected_template, checked_against } — the corrected template is a ready-to-sign payload for this fleet: network eip155:8453 (Base), asset USDC 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913, payTo 0x198f3895551B309fF5C5F59e690FB0823d10EA93.
| Class | Meaning |
|---|---|
| expired | The authorization's validity window has passed (or has not started). The #1 killer: a 300-second window plus clock skew. |
| wrong-network | Signed for a chain other than Base mainnet (eip155:8453). |
| wrong-asset | The payment asset is not USDC on Base. |
| wrong-payee | authorization.to / accepted.payTo is not the seller's address. |
| amount-mismatch | authorization.value differs from the amount in the 402 requirements (atomic units, 6 decimals). |
| malformed | Not valid JSON/base64, missing authorization fields, or no signature. |
| unknown | Structurally valid — the failure is facilitator-side (balance, nonce reuse, EIP-712 domain). The response lists what to check. |
Built by Mekong Trade Intelligence — pay-per-call APIs for AI agents, settled in USDC on Base. Discovery: openapi.json · /.well-known/x402