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

No annotations are provided, so the description carries the full burden of disclosing behavior. It does add one useful trait—'No browser is launched'—but it omits how the check is performed, what 'can be opened' means, failure modes, side effects, or whether any network request occurs. This is a significant transparency gap.

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 or repetition. The most behaviorally important caveat, 'No browser is launched,' is front-loaded immediately after the main action, so every word earns its place.

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?

Given no output schema, no annotations, 9 optional parameters, and a large sibling set, this description is too thin. It does not explain return values, success criteria, what 'ok' means, or how this tool relates to similar URL-oriented siblings, so an agent cannot fully anticipate the tool's behavior.

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 has 100% description coverage across all 9 parameters, so the baseline is 3. The tool description adds no parameter-level meaning and does not identify which parameter is the primary input, but the schema descriptions already provided detailed per-parameter context.

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 action ('Check whether a URL can be opened') on a clear resource, and adds a clarifying behavioral qualifier ('No browser is launched'). However, it does not explicitly differentiate itself from the similarly named sibling tool browser-url-ok, which prevents a top score.

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 offers no guidance on when to use this tool versus alternatives like browser-url-ok, fetch-status, normalize-url, or web-fetch. There are no exclusions, preconditions, or selection criteria beyond the obvious purpose implied by the action.

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