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

With no annotations, the description carries the behavioral burden. It does disclose one significant trait: no browser is launched, which is useful and safety-relevant. However, it does not say whether it makes a network request, what 'can be opened' means, or what the result looks like.

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 every word earning its place. The main behavior is front-loaded and the important 'no browser' caveat follows immediately.

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?

The tool has 9 parameters, no output schema, and no annotations, so the description must explain more than it does. It does not define what 'can be opened' means or what the tool returns, nor does it clarify how the non-URL optional parameters relate to the core check. An agent is left to guess the return contract and success criteria.

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 schema provides descriptions for all 9 parameters, so the baseline is 3. The description adds no new parameter meaning beyond reinforcing that `url` is the central input, but it does not compensate for the ambiguity around the many optional discarded fields.

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 says 'Check whether a URL can be opened', giving a clear verb, resource, and expected outcome. 'No browser is launched' adds a useful qualifier. It does not explicitly name or contrast sibling tools such as browser-url-ok or fetch-status, so it misses the full differentiation needed for a 5.

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 guidance about when to use this tool versus alternatives like browser-url-ok, fetch-status, or normalize-url. The description does not provide context for selecting it or mention what to do in other situations.

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