Diagnose x402 seller endpoints: what is wrong with your 402 challenge, and how to fix it.
Scored across 3 tools
Each tool has a clearly distinct purpose: probe_x402_endpoint performs the actual endpoint test, list_checks provides the rule table, and explain_defect offers detailed explanations for a specific rule. No overlap or ambiguity.
All tool names follow a consistent verb_noun pattern in snake_case (explain_defect, list_checks, probe_x402_endpoint), making the naming predictable and easy to understand.
With three tools, the server is well-scoped for its purpose: probe to test, list to see all rules, explain to get details on a specific rule. The count is appropriate without being too thin or excessive.
The tool set covers the full workflow for x402 endpoint diagnosis: testing the endpoint, listing all possible checks, and explaining any defect. There are no obvious gaps—the combination of probe, list, and explain is complete for the domain.
Full explanation of one rule by id — what it checks, why it matters, how to fix it, and where the rule came from. Use when you want the reasoning without re-probing.
Inputs: id (required).
The whole rule table. Knowing what was NOT checked is part of knowing what a clean result means.
Inputs: no named parameters.
Probe an x402 seller endpoint and report what it observes about it. Performs the handshake a paying client would: GET with no X-PAYMENT header, then checks the 402 challenge against 16 rules. Every finding says whether the rule comes from the x402 spec or from an observed facilitator rejection. Reports status "healthy" (nothing to report), "advisories" (only warn/info findings — the endpoint works), "defects_found" (at least one error-severity finding), "not_x402" or "unreachable".
Inputs: url (required).
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
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Free x402 endpoint linter: unpaid 402 challenge, payTo/asset/amount, CORS, directory readiness.
Lints whether a paid API's 402 response speaks the x402 protocol correctly.
Check an x402 endpoint's payment challenge and discovery metadata before paying.
x402 endpoint doctor: grades a paid route A-F unpaid, with paste-ready fixes. By Crypto Money Maker
Add one secure layer between your agents and this server.