check_x402_url

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

With no annotations provided, the description carries the full burden. It discloses that no credential is required, that it is a public probe with IP rate-limiting, and explains the exact return shape for both plain and x402-protected URLs. This is comprehensive behavioral transparency for a read-only probe.

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 three concise sentences, each earning its place: the first states the core function, the second describes behavior and return format, and the third gives a specific use case. It is front-loaded and free of unnecessary detail.

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 single-parameter tool with no output schema, the description is complete. It covers the return shape, authentication requirements, rate limiting, and a concrete usage scenario, making it fully self-contained for an agent to select and invoke correctly.

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?

Schema coverage is 100% for the single 'url' parameter, which has a clear description 'Target URL to probe.' The tool description does not add parameter-specific meaning beyond the schema, so the baseline score of 3 applies.

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 checks whether a URL is x402-protected and what it costs, using the specific verb 'Check' and resource 'URL'. It distinguishes itself from sibling tools like x402_pay by emphasizing it's a public probe without credentials, making its purpose unique and unambiguous.

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 explicitly provides a use case: 'Use to vet a vendor before minting keys or funding.' It implies when to use (when you need to assess a URL without credentials) but does not explicitly name alternatives or when-not-to-use, so it falls slightly short of full guidance.

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