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

With no annotations, the description must carry the behavioral disclosure, but it only reveals that no browser is launched. It does not disclose whether a network request is made, whether the check is read-only, what side effects might occur, how return values look, or whether errors are thrown for invalid URLs. One behavioral fact is provided, but significant behavioral context is missing.

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 extremely concise: two short sentences, no filler, and the core purpose is front-loaded. Every word contributes to the intended meaning.

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?

This tool has 9 optional parameters, no annotations, and no output schema, yet the description only provides a one-line purpose and a single behavioral caveat. It does not explain what 'can be opened' means, what the tool returns, how URL checking relates to the other accepted parameters, or when to prefer it over sibling tools.

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 description coverage is 100%, so the schema already documents all 9 parameters. The tool description adds no parameter-level meaning beyond the schema, which is acceptable under the baseline but adds no extra value here.

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 action ('Check whether a URL can be opened') and a concrete resource (URL). The added phrase 'No browser is launched' offers a useful distinction from browser-centric alternatives, though it does not explicitly name a sibling tool or clarify how this differs from normalize-url or fetch-status.

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?

There is no explicit guidance about when to use this tool versus alternatives like browser-url-ok, normalize-url, or web-fetch. The phrase 'No browser is launched' hints at a lightweight check, but the description never states conditions, exclusions, or preferred use cases.

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