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

No annotations are present, so the description carries the full burden of behavioral disclosure. It discloses one useful trait: no browser is launched. However, it does not explain whether a network request occurs, whether the operation is read-only, what 'opened' means, or what response the agent should expect.

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, purposeful sentences. The main action is front-loaded, and the 'No browser is launched' caveat adds relevant clarification without wasted words.

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 that the schema includes varied parameters (ref, city, feed, host, json, path) and there is no output schema or annotations, the description is far too thin. It does not explain how these parameters relate to 'checking whether a URL can be opened,' nor what result or side effects are expected.

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 provides descriptions for all eight parameters, many with clarifying notes like 'discarded after the shape check' or 'discarded after the call,' so schema coverage is high. The tool description adds no parameter-level detail, but the schema carries the load; the baseline of 3 is appropriate.

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.' This is more specific than a tautology and immediately signals the tool's primary function. However, it does not explicitly differentiate from siblings like fetch-status or normalize-url, and 'can be opened' leaves the exact criteria (shape check, HTTP reachability, browser compatibility) ambiguous.

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 only the basic intent—checking URL openability—and adds one negative constraint ('No browser is launched'). It provides no guidance on when to prefer this tool over close alternatives such as fetch-status, playwright-url-ok, or normalize-url, and it does not mention any prerequisites or exclusions.

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