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

With no annotations, the description carries the burden of behavioral disclosure. It does disclose one meaningful trait: no browser is launched, implying the check is not a full browser render. However, it does not state whether a network request is made, whether the check is purely syntactic, what side effects occur, or what the response looks like.

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 filler and front-loads the core purpose. The no-browser constraint earns its place as a key distinguishing behavioral note. Despite being under-sized for the tool's complexity, the wording is maximally efficient.

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?

There is no output schema, no annotations, 9 optional parameters, and 27 sibling tools, so the description must do more work. It does not explain what result is returned, which parameters to supply for which use case, or how this tool differs from URL-related siblings. Significant gaps remain for an agent to invoke it correctly.

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 schema already documents each parameter. The tool description adds no parameter-level meaning beyond the word 'URL' and does not explain why non-URL parameters such as ref, city, json, path, zone, or query exist. It may even mislead an agent about the tool's full scope.

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,' which is clear. The additional 'No browser is launched' differentiates it from a full browser-based check and hints at a distinction from browser-url-ok. However, the input schema accepts nine heterogeneous parameters, so the URL-only framing is narrower than the actual interface and leaves ambiguity about how the check is performed.

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 gives no guidance about when to use this tool versus alternatives like browser-url-ok, fetch-status, normalize-url, or web-fetch. 'No browser is launched' is an implementation detail, not a routing rule. An agent cannot tell which URL-related sibling is the right choice.

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