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

With no annotations, the description is the only behavior source, and it does disclose two meaningful traits: the body is discarded and only public URLs are in scope. It does not mention network side effects, error behavior, redirects, or the fact that non-url parameters are ignored. This is adequate but leaves several operational gaps.

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?

Two short sentences with no filler, and both sentences carry useful information: what is returned and what is not. The key constraint, 'Body discarded', is front-loaded in the second sentence. Nothing extraneous is present.

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?

Despite 9 optional parameters, no required parameters, no output schema, and no annotations, the description only covers URL status/content-type checks. An agent cannot tell whether the other eight parameters are alternate invocation modes or distractors, nor what the response/error format looks like. This is not complete enough for reliable invocation in ambiguous cases.

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 description coverage is 100%, so the schema already documents each parameter's meaning and even notes discarded values, establishing the baseline of 3. The description adds no parameter-level information beyond the notion of a public URL. It also does not tell the agent which of the nine optional parameters is the relevant one for the stated purpose.

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 concrete result: HTTP status and content type for a public URL, and adds that the body is discarded, which gives the agent a clear sense of the operation. It does not explicitly contrast siblings like fetch-status or browser-url-ok, but the 'body discarded' qualifier differentiates it from content-returning fetches. The presence of nine unrelated optional parameters in the schema is not reflected in the description, so this is clear but not fully complete.

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 phrase 'public URL' and 'Body discarded' imply when the tool is appropriate and when it is not: it is for lightweight URL checks, not for retrieving page content or private URLs. However, the description gives no explicit alternatives or conditions, even though siblings such as fetch-status and browser-url-ok exist. The guidance is mostly implied rather than stated.

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