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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds the unique behavioral trait that the tool charges 0.0001 XNO via x402, which is essential for an agent to decide whether to invoke. This cost disclosure goes beyond the annotations and schema.

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 a single, dense sentence that front-loads the action and immediately discloses the cost. Every word earns its place, and there is no redundant filler. This is ideal for an agent scanning tool definitions.

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?

The tool is simple: one well-documented parameter, an output schema, and annotations covering safety and idempotency. The description adds the essential cost detail. Its only notable gap is the lack of differentiation from check_url_status, which is a minor completeness issue for an agent deciding between tools.

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 input schema provides 100% coverage for the single 'url' parameter, including a clear description of what counts as a valid http(s) URL. The description adds no additional parameter semantics beyond restating the purpose and implying no restrictions. A baseline of 3 is appropriate given the schema's thoroughness.

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 states a specific verb ('Check') with three concrete resources (HTTP status, response time, redirect chain) for any URL, which clearly identifies the tool's action and scope. It does not explicitly differentiate from the closely named sibling check_url_status, so it misses the top score for sibling distinction.

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 offers no guidance on when to choose this over check_url_status or other sibling tools. It simply says 'any URL' without stating prerequisites, exclusions, or preferred use cases. An agent would have to infer which tool to use for a given scenario.

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