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

With no annotations, the description carries the entire behavioral burden, but it only reveals that no browser is launched. It does not clarify what 'can be opened' means, whether any network request is made, what is returned, or how the many unrelated-looking parameters are handled.

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 extremely concise: two short sentences, no filler, and the primary purpose is stated first. The additional behavioral note about not launching a browser earns its place by clarifying the tool's non-destructive nature.

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?

This tool has nine optional parameters and no output schema, yet the description offers no invocation pattern, return format, or explanation of how the parameters relate to the URL check. The schema documents each parameter, but an agent still lacks enough context to know how to call this tool confidently.

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 individual parameter descriptions already document each field. The tool description adds little parameter-level meaning beyond singling out URL-related checking, but it does not need to compensate because the schema is already thorough.

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 ('Check') and resource ('whether a URL can be opened'), which gives a basic sense of the tool's purpose. It does not differentiate this tool from siblings like playwright-url-ok or normalize-url, but it is more than merely restating the tool name.

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?

There is no guidance on when to use this tool versus alternatives such as playwright-url-ok, normalize-url, or fetch-status. The phrase 'No browser is launched' implies a non-browser check, but no explicit conditions or exclusions are provided.

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