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

With no annotations, the description must carry behavioral weight. It does convey that the operation is read-only (HEAD over a public URL) and that no content is returned, which is useful. However, it omits details like redirect handling, error behavior, timeouts, or what exactly the returned status looks like.

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, front-loaded sentence: 'HEAD a public URL and return status only.' It contains no fluff, no tautology, and every word adds value.

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 has 9 optional parameters with no output schema, and the description gives an agent almost no context to choose the right parameter. The `url` property's schema description says 'HTTPS URL to normalize or cite,' which conflicts with the HEAD behavior described. The description is not sufficient to ensure correct invocation.

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 structured fields already document each parameter. The description adds no extra parameter-level meaning—it never indicates that `url` is the actual input to use or that the other parameters are irrelevant/ignored. Baseline 3 is correct because the schema carries the information.

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 action (HEAD a public URL) and the result (return status only), which distinguishes it from content-fetching tools like `web-fetch`. However, it does not explicitly differentiate itself from sibling tools, and it leaves 'status' ambiguous—HTTP code vs. plain text—so it is a clear purpose but not fully differentiating.

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?

There is no guidance on when to use `fetch-status` versus the many sibling tools, nor any direction on which of the 9 optional parameters should be supplied. The description does not say that only `url` is relevant or that the other parameters are discarded, leaving the agent with no selection rule.

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