check_url

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

No annotations are provided, so the description carries the full burden. It discloses the HTTP method (HEAD) and the general behavior (accessibility check, header inspection), but does not mention error handling, redirects, timeouts, or any side effects. For a network tool, this is a moderate transparency gap.

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, focused sentence that front-loads the verb and clarifies the purpose. It contains no filler or redundant information.

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 parameter, output schema available). The description provides enough context for an agent to select and invoke it correctly, and the sibling list does not introduce ambiguity that would require further explanation.

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 schema describes the only parameter 'url' with 'The URL to inspect' at 100% coverage. The tool description adds no extra semantic meaning to the parameter beyond what the schema already provides, so the baseline of 3 is appropriate.

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 ('Send an HTTP HEAD request') and the resource ('URL'), with a specific purpose: 'verify URL accessibility and inspect response headers.' This distinguishes it from siblings like http_get and fetch_page, which imply different HTTP methods or full-page fetching.

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 'to verify URL accessibility and inspect response headers' provides clear context for when to use this tool—when a lightweight HEAD request is appropriate. However, it does not explicitly name alternatives or exclusions, so it misses the top tier of guidance.

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