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

There are no annotations, so the description carries the behavioral disclosure burden. 'No browser is launched' is a meaningful side-effect guarantee, but the description does not state whether the tool makes network requests, only validates shape, returns a boolean, or how failures are reported.

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: the core action is front-loaded and the key safety clarification follows immediately. Every word serves a purpose.

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?

Despite the schema documenting parameters, the definition lacks an output schema and the description omits return behavior, interpretation of 'can be opened,' and selection criteria relative to related tools. For a tool with seven parameters and several siblings, this is not enough for an agent to call it 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?

The input schema describes all seven parameters in detail, including their roles and whether they are discarded, so schema coverage is high. The description adds no parameter-level meaning, which aligns with the baseline of 3 when the schema already documents the parameters.

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 names a specific verb ('check') and a clear resource ('whether a URL can be opened'), and the 'No browser is launched' clause helps distinguish it from browser-launching tools like playwright-url-ok. However, 'can be opened' is somewhat ambiguous—it does not clarify whether this is a syntax/shape check or a reachability check—and the schema's many non-URL parameters are not reflected in the description.

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 explicit guidance on when to use this tool versus siblings such as normalize-url, fetch-status, or playwright-url-ok. The 'No browser is launched' clause implies a lightweight, non-browser check, but no conditions, exclusions, or alternative-selection rules are stated.

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