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x402Fix: x402 endpoint doctor

check_x402_endpoint

Read-onlyIdempotent

x402 endpoint doctor: probes a paid x402 URL unpaid (never pays) and grades it A-F: 402 on GET / HEAD / empty POST, CORS, v2 PAYMENT-REQUIRED header and v1 body, accepts (USDC asset, EIP-712 domain, Solana feePayer, amounts, payTo), multichain consistency and the Bazaar declaration. Free preview tier: grade, score, status and counts. The paid x402 endpoints /v1/lite ($0.005), /v1/check ($0.02, adds the facilitator validate verdict, payee checks and generated fixes) and /v1/site ($0.05, whole origin) return the fix list.

[x402Fix via YourAITools MCP Hub] Free tier: same as x402Fix's own MCP server (call without payment and without tier). Paid: lite $0.005 / check $0.02 / site $0.05 per call, with a credits key (Authorization: Bearer yatc_...) or x402 (USDC; the hub returns the payment terms). Failed tool calls aren't charged: credits are refunded automatically and x402 payments only settle on success.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>"
    },
    "name": "check_x402_endpoint"
  }
}

Input Schema

Name	Required	Description	Default
`url`	Yes	Full https URL of the paid x402 route (site tier: the origin or API base URL)
`tier`	No	Paid tier: lite $0.005, check $0.02, site $0.05. Omit tier (with no credits key or x402 payment) to use the free tier.
`method`	No	Method your paid route uses (default: from its Bazaar declaration, else GET)
`framework`	No	(paid calls only)	hono

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 30, 2026
- addedInput schema / properties / method / examples
```
Added value: +[
+  "GET"
+]
```
- addedInput schema / properties / url / examples
```
Added value: +[
+  "https://api.switch402.com/v1/scrape?url=https://example.com/"
+]
```
First observedOct 24, 2026

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial extra context: it never pays, probes unpaid, failed calls aren't charged, credits refunded, x402 settles only on success, and the auth model (Bearer yatc_ or x402). This is rich behavioral disclosure beyond what annotations provide.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core purpose and inspection list, and the tier/pricing detail is genuinely relevant. It runs long, with the hub billing footer adding bulk, but nearly every clause carries useful information rather than filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description carries the return-value burden and does so: free preview returns grade/score/status/counts, paid tiers add fix list (and validate verdict/payee checks for check). An agent has enough to select a tier and interpret results.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, and the description does add meaning: it explains the free tier is selected by omitting tier with no key/payment, and that method defaults from the Bazaar declaration. Framework's '(paid calls only)' note also clarifies semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (probes, grades) and a specific resource (a paid x402 URL), plus exactly what it inspects: 402 on GET/HEAD/POST, CORS, PAYMENT-REQUIRED header, accepts, multichain consistency, Bazaar declaration. An agent can easily tell it apart from siblings like check_mcp_server or audit_website.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Lays out a clear free-vs-paid tier decision with pricing and what each tier adds (lite vs check vs site), which is strong usage context. It doesn't explicitly contrast against sibling checks (e.g. check_mcp_server), so it's clear context without exclusions.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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