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x402 Doctor

by twelvepermissions.com · remote · no sign-in to list tools · v1.0.0 · published by com.twelvepermissions

Diagnose x402 seller endpoints: what is wrong with your 402 challenge, and how to fix it.

Changes · 1
CompareRegistry entry

3 tools: 1 change things and 2 only read.

Scanned Oct 21, 2026

No check matched anything in the tool definitions. No finding is not a safety guarantee. How the checks work.

claude mcp add --transport http x402-doctor https://x402-doctor.tsharpe.workers.dev/mcp

Tools

Open a tool for its reasons and full description. Descriptions are the publisher's own words, shown as they are.

3 tools

Changes things 1Claude Code: ask
  • probe_x402_endpointProbe an x402 seller endpoint and report what it observes about it.No findings

    Why it is in this group

    • Nothing in its name or description says what it does, so it is counted as a write.
    Description, as the server wrote it
    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".
Only reads 2Claude Code: allow
  • explain_defectFull explanation of one rule by id — what it checks, why it matters, how to fix it, and where the rule came from.No findings

    Why it is in this group

    • The name "explain_defect" says "explain": a word for reading.
    Description, as the server wrote it
    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.
  • list_checksThe whole rule table.No findings

    Why it is in this group

    • The name "list_checks" says "list": a word for reading.
    Description, as the server wrote it
    The whole rule table. Knowing what was NOT checked is part of knowing what a clean result means.

This is not a safety rating, and no finding is not a safety guarantee. The groups and findings come from fixed checks of the tool definitions the server returned on the date shown, not from its code or what it does when called. How the checks work.

Install

Pinned to version 1.0.0. Values in angle brackets are yours to fill in.

claude mcp add --transport http x402-doctor https://x402-doctor.tsharpe.workers.dev/mcp

Run in a terminal.

Claude Code permissions

Allow the reads, ask before a change, deny the deletes. Paste into .claude/settings.json.

.claude/settings.json
{
  "permissions": {
    "allow": [
      "mcp__x402-doctor__explain_defect",
      "mcp__x402-doctor__list_checks"
    ],
    "ask": [
      "mcp__x402-doctor__probe_x402_endpoint"
    ],
    "deny": []
  }
}

Tools that only read are allowed, tools that change things ask first, tools that delete or cancel are denied. It assumes the server is installed as x402-doctor. Review it before you use it.