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

With no annotations, the description carries the transparency burden. It discloses a key behavioral trait: the response body is discarded, so only status and content type are returned. It also scopes input to public URLs, implying no authentication, but it does not mention redirect behavior, timeouts, or error response handling.

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 extremely concise and front-loaded: it states the purpose in the first sentence and adds the key behavioral caveat in the second. There is no filler or redundancy.

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 definition is incomplete given the tool's complexity: nine optional parameters, no annotations, no output schema, and a description that only covers URL fetching. An agent cannot confidently determine which parameter to supply, what the response structure looks like, or how unrelated parameters will be handled.

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?

Although schema description coverage is 100%, the parameter descriptions conflict with the tool's stated purpose. Most parameters refer to unrelated concepts like git refs, city names, JSON validation, or timezones and are 'discarded after the shape check,' while the description only discusses fetching a URL. The description does not clarify that only the 'url' parameter is relevant, leaving the input contract ambiguous.

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 identifies the tool's function: retrieving HTTP status and content type for a public URL, with the body discarded. This distinguishes it from tools that return full content or perform other URL operations, though it does not explicitly name a sibling alternative.

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 gives no explicit guidance on when to use this tool versus siblings like fetch-status, browser-url-ok, or normalize-url. It implies use for public URLs and header-only checks via 'Body discarded,' but it never states exclusions or recommends alternatives.

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