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

With no annotations, the description carries the full burden of behavioral disclosure. It does state 'No browser is launched,' which is a useful safety note, but it fails to disclose what happens with the many other parameters (e.g., whether city or json are validated, what 'discarded after the shape check' means), what the return value is, or any side effects or error conditions. The description is largely silent on behavior beyond that one clause.

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, concise sentence, which is structurally efficient. However, it is under-specified for the tool's complexity: with 9 optional parameters and no annotation or output schema, one sentence is not appropriately sized. The conciseness is good, but the content is inadequate, so a middle score is appropriate.

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?

For a tool with 9 parameters, zero annotations, and no output schema, the description is completely inadequate. It does not explain what the tool does with the variety of inputs (city, json, path, zone, query), how they relate to 'checking a URL,' or what the result looks like. An agent cannot reasonably call this tool correctly based solely on the description and schema.

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 baseline is 3. The tool description adds no meaning beyond what the schema already provides; each parameter has a description in the schema, but those descriptions are cryptic (e.g., 'discarded after the shape check') and the tool description does not clarify their semantics or relationship to the stated purpose. Thus no bonus is warranted, and the baseline holds.

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 clear verb and resource ('Check whether a URL can be opened'), but the input schema accepts many non-URL parameters (city, feed, json, path, zone, query) with no explanation, making the stated purpose misleading. It also fails to differentiate from sibling tools like playwright-url-ok, normalize-url, or fetch-status, so an agent cannot reliably select it.

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?

No guidance is provided on when to use this tool versus alternatives. The description does not mention any exclusion criteria or context that would help an agent decide between this and siblings like web-fetch or playwright-url-ok. There is no implied usage beyond the one-sentence purpose, and no 'when not to use' statement.

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