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

With no annotations available, the description carries the burden of behavioral disclosure. It does disclose a meaningful side-effect: no browser is launched. However, it does not describe what happens when the URL cannot be opened, whether a network request is made, or what kind of result is returned.

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, front-loaded sentences with no filler. 'No browser is launched' earns its place by preventing confusion with browser-based alternatives.

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 exposes seven input parameters and has no output schema or annotations, yet the description says nothing about which parameters matter, what a successful check returns, or how failures are reported. An agent can likely guess the basic url case but has no grounding for edge cases or the broader schema.

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?

The input schema already has descriptions for all seven parameters, so schema description coverage is high and the baseline applies. The description adds only the notion of URL checking but does not explain how the many non-URL parameters relate to the tool; the schema's own 'url' description is also oddly focused on normalization/citation rather than checking openness.

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 verb and resource: 'Check whether a URL can be opened.' The addition 'No browser is launched' helps distinguish it from browser-dependent siblings such as playwright-url-ok, though it does not explicitly name that alternative or clarify what 'opened' means (syntactic validity vs. actual reachability).

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 'No browser is launched' sentence provides an implicit usage signal that this is a lightweight or non-browser option. However, there is no explicit guidance about when to use this tool versus fetch-status, web-fetch, or normalize-url, so the routing context is only implied rather than stated.

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