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

With no annotations, the description bears full responsibility for disclosing behavior. It reveals one useful trait ('No browser is launched') but leaves fundamental questions unanswered: what does 'can be opened' actually verify (syntax, DNS, HTTP response)? It does not mention network usage, side effects, or what is discarded versus 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?

A single, front-loaded sentence with no filler. It states the core action and the key non-behavior in just eight words, every one of which 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?

For a tool with 8 parameters, no output schema, and no annotations, this description is inadequate. It fails to clarify which parameters are relevant, what the function returns (e.g., boolean, status), and how this check differs from overlapping siblings like normalize-url or fetch-status. The description alone would not let an agent reliably select and invoke this tool.

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 provides descriptions for all 8 parameters, giving high schema coverage. The description itself adds no parameter-level meaning, but the baseline remains 3 because the schema already documents each field. The description's silence on how parameters like 'city' or 'json' relate to a URL check is a gap, but it does not lower the score below the coverage-based baseline.

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 ('Check') and resource ('whether a URL can be opened'), and the clause 'No browser is launched' differentiates it from browser-launching tools like playwright-url-ok. It does not explicitly name siblings or clarify the full scope, so it is clear but not maximally distinguishing.

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 implies the tool is for lightweight URL checks without browser launch, but it provides no explicit when-to-use guidance, no exclusions, and no mention of alternatives among the many sibling tools (normalize-url, fetch-status, web-fetch). Agents would have to infer the appropriate context.

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