Agent Payment Error Preview
Use this skill when an agent-payment integration is failing and you need a fast first-pass classification before deciding whether to install the paid ClawMart diagnoser.
What this free preview does
Classify a failure into one likely family using the visible symptom:
| Symptom | Likely family | First check |
|---|---|---|
| Repeated HTTP 402 after resubmitting payment | x402 retry loop | Compare chain id, USDC contract, validity window, and facilitator status. |
HTTP 401 after X-PAYMENT / payment signature |
signature/auth mismatch | Recover signer; verify EIP-712 domain and signing wallet. |
| HTTP 409 or on-chain reused authorization | nonce/idempotency conflict | Use a fresh nonce and content-bound idempotency key. |
AP2/MPP/ACP expired or out_of_scope |
mandate/scope mismatch | Reissue mandate with correct merchant, amount, and validity window. |
| MCP tool unavailable after discovery | manifest/tool drift | Re-fetch MCP manifest and match by capability, not hard-coded tool id. |
| 502/504 during settlement | facilitator/RPC transient | Back off with jitter; do not blindly re-sign if body says permanent failure. |
Minimal workflow
- Capture request method, URL, status, response body,
Payment-Required/X-Payment-Responseheaders, facilitator response, and chain tx hash if any. - Identify the protocol:
x402,AP2,ACP,MPP,TAP, or MCP tool invocation. - Map the symptom with the table above.
- Apply the first check once.
- If the answer is still ambiguous, use the paid ClawMart package below for a structured diagnosis against the live corpus.
Paid upgrade path
Install Agent Payment Error Diagnoser on ClawMart when you need machine-readable diagnosis, family ranking, remediation steps, and live corpus-backed examples:
https://www.shopclawmart.com/listings/agent-payment-error-diagnoser-adda0b18
Backend used by the paid package:
https://agent-payment-error-corpus.mtree.workers.dev/v1/agent-payments/diagnose_error— x402 paid diagnosis endpointhttps://agent-payment-error-corpus.mtree.workers.dev/v1/agent-payments/error_families— x402 paid family catalog endpoint
Safety limits
- Do not paste private keys, raw wallet seeds, bearer tokens, or unredacted authorization headers.
- Do not retry payments indefinitely; use a max retry counter and stop immediately on permanent signature/scope errors.
- Do not assume every 402 is an error; in x402 it is the normal first step unless it repeats after payment.
Anti-patterns
- Treating HTTP 401 like a normal API-key failure without checking EIP-712 domain mismatch.
- Reusing EIP-3009 nonces across attempts.
- Caching an agent-payment mandate or session token across merchants.
- Hard-coding MCP tool IDs instead of refreshing manifests per session.