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

With no annotations, the description carries the transparency burden. It reveals only that no browser is launched; it does not disclose that a network request may be made, whether it is read-only, or what success/failure 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 only two short sentences with no redundant phrasing. It is concise, though it sacrifices needed detail.

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 gives no output schema, no return-value description, no error conditions, and no indication of which of the nine optional parameters are actually relevant. An agent cannot infer what arguments to provide or how to interpret the result.

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?

Although every parameter has a description, most are unrelated to checking a URL (ref, city, feed, zone) and several are described as discarded. The main 'url' parameter is described as 'normalize or cite' rather than 'open', so the parameter descriptions actively mislead about how to call the tool.

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 clear action ('check whether') and resource ('a URL'), and 'No browser is launched' distinguishes it from browser-based alternatives. It is somewhat vague about what 'opened' means (HTTP status? reachability?), but the core purpose is identifiable.

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 given for when to prefer this tool over siblings such as browser-url-ok, fetch-status, or normalize-url. 'No browser is launched' is a constraint, not a usage condition.

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