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 discloses one useful trait ('No browser is launched'), but it does not explain how 'can be opened' is determined—whether a network request is made, whether it is read-only, what side effects occur, or what the return value looks like. This is a significant gap for a tool that presumably performs network checks.

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 exceptionally concise: two short sentences totaling ten words. It front-loads the core purpose and immediately clarifies the key behavioral constraint. There is no filler or redundancy.

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 description is far too thin for a tool with nine diverse optional parameters and no output schema. It does not explain why parameters like city, json, path, or zone appear in a URL-checking tool, how they are discarded, or what the caller should pass. The schema notes help, but the overall definition leaves crucial context missing for an agent to confidently select and invoke the tool.

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 schema already documents all nine parameters with detailed notes (e.g., 'discarded after the shape check', 'no disk access'). The tool description itself adds no parameter-level meaning, which means it stays at the baseline of 3. It does not harm clarity because the schema is rich enough.

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 a specific action and resource: 'Check whether a URL can be opened.' It also adds a distinctive behavioral note, 'No browser is launched,' which helps set it apart from sibling tools like playwright-url-ok. However, it does not explicitly distinguish it from other URL-related siblings such as fetch-status or web-fetch, so it falls just short of a 5.

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 provides no guidance on when to use this tool versus alternatives. 'No browser is launched' implies a lightweight check, but there is no mention of when not to use it or which sibling tool should be chosen for browser-dependent or fetch-intensive scenarios. With many URL-related siblings, this omission leaves the agent to guess.

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