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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It does state the no-browser behavior and says it's a check for whether the URL can be opened, but it gives no detail about the network access, timeout, redirects, or how the result is returned (boolean? status code?). With 9 parameters including city/json/path/zone, it does not explain how these are treated or conflict with the url-only focus. This is a significant gap for a tool with zero annotation coverage.

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 two-sentence, front-loaded with the purpose and the key non-browser trait, with no redundant phrases. It is compact and immediately readable. Structure is optimal for the information provided.

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 and no output schema, no annotations. The description only covers a single URL check, leaving the role of the other 8 parameters unexplained, and it does not describe return values or behavior beyond the check. Given the schema's complexity, the description is too thin to tell an agent how to supply the correct input or interpret the result. The discarding notes in schema descriptors are not sufficient to make the tool usable.

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 the schema — it doesn't mention which parameters to use, that the others are discarded, or why they are present. The schema descriptions already say some params are discarded, but the description doesn't reinforce, so no value is added. The description's value is neutral.

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 action and resource: 'Check whether a URL can be opened.' The 'No browser is launched' clause distinguishes this tool from browser-based alternatives like playwright-url-ok, providing purpose clarity beyond just restating the name. However, the purpose is not narrowed to a single parameter, and the existence of 8 other input params creates ambiguity about what the tool actually operates on.

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 description includes 'No browser is launched,' which labels when to use the tool versus a browser-based sibling, but it does not explicitly state alternatives or conditions. There is no mention of when to use this tool over web-fetch, normalize-url, or the other shape types in the schema, and no guidance about which parameters to provide. It would be an implicit hint for a browser test, but not clear, so usage guidance is minimal.

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