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

The description mentions one behavioral aspect ('No browser is launched') but does not disclose side effects, error behavior, or read-only guarantees. More importantly, it does not explain why the schema accepts nine mostly unrelated parameters, leaving the actual behavior of the tool unclear.

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 short and free of unnecessary words; both sentences contribute information. It could be slightly more explicit, but it is not verbose or redundant.

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?

With nine parameters, no output schema, and no explanation of return values, success/failure conditions, or why most parameters are accepted, the description is far from complete. The mismatch between the described purpose and the parameter list leaves critical context missing.

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 descriptions cover individual parameter names, but the tool description adds no meaningful parameter guidance and actually conflicts with the schema: the description implies a URL-only check, while the schema includes git refs, city names, JSON text, timezones, and search queries. An agent cannot confidently determine which parameters are relevant from the description alone.

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 clearly states the action ('Check whether a URL can be opened') and the resource (URL), and the added note 'No browser is launched' helps distinguish it from browser-based sibling tools. However, 'opened' is somewhat ambiguous about whether this is an HTTP reachability check, a validation check, or a rendering check.

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?

No guidance is provided about when to choose this tool over closely related siblings like browser-url-ok, fetch-status, or normalize-url. The description gives a trait ('No browser is launched') but does not state explicit use conditions or alternatives.

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