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

With no annotations, the description must carry the full behavioral burden. It only discloses 'No browser is launched,' but fails to mention that most parameters are 'discarded after the shape check' or that no disk access occurs (though these are in the schema). It does not state whether the operation is read-only or has side effects, nor what the tool does with the other parameter types.

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 two short sentences with no fluff, front-loading the core purpose. It is concise, though the brevity contributes to the completeness problem.

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 optional parameters, no output schema, and no annotations, the description is severely incomplete. It only addresses URL checking, leaving the agent unaware of how to use the tool for other input types (city, feed, json, etc.) and what the expected outcomes are. This is insufficient for a tool of this complexity.

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 coverage is 100%, so each parameter has a description that adds semantic value (e.g., 'discarded after the shape check', 'no disk access'). The tool description itself adds no parameter-level meaning, so the baseline of 3 applies. The description does not clarify how parameters relate to 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 specific verb and resource ('Check whether a URL can be opened') and notes no browser is launched, but the input schema exposes 9 unrelated parameters (city, feed, json, path, zone, query, etc.) that are not mentioned. This makes the actual scope ambiguous and potentially misleading about what the tool validates.

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 the many siblings (e.g., browser-url-ok, fetch-status, normalize-url, validate-json). There is no mention of alternatives or exclusion criteria, leaving the agent to guess which tool fits.

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