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

With no annotations provided, the description bears the full burden of disclosing behavior. It clearly states the HTTP method, the conditional behavior on HTTP 402, the return type (parsed accepts[]), the HTTPS-only restriction, and that no signing is performed. However, it does not describe what happens if the response is not HTTP 402, leaving a minor gap.

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

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

The description is two sentences, front-loaded with the core action, and every word adds value. It efficiently conveys the purpose, conditional behavior, return value, and constraints without unnecessary elaboration.

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

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

For a tool with one parameter, no output schema, and no annotations, the description covers the essential aspects: what it does, when it returns data, security constraints, and its non-signing nature. The only missing piece is the explicit behavior for non-402 responses, which is a minor gap for full completeness.

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

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

The schema already provides full coverage for the single parameter (url) with a clear description. The tool description reinforces the HTTPS requirement but adds no new semantic details beyond what the schema already contains, so the baseline score of 3 is appropriate.

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

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

The description clearly states the tool's function: perform a GET request on a candidate x402 URL and, if HTTP 402 is returned, parse and return the payment requirements (accepts[]). It distinguishes itself from sibling tools like bazaar_pay_and_call by emphasizing that this tool only probes and does not pay.

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

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

The description implies the tool should be used to assess a URL's payment requirements before deciding whether to pay, positioning it as a precursor to payment. It also sets constraints (HTTPS only, no signing) that guide appropriate usage, but it does not explicitly mention alternatives or exclusions.

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