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

The description discloses one behavioral trait: no browser is launched. But with no annotations, it carries the full burden of explaining side effects; it does not say whether a network request is made, whether the check is purely syntactic, or what error conditions may arise.

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 concise: two short sentences with no wasted words. The 'No browser is launched' caveat is useful and earns its place, though the brevity leaves important details unstated.

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 9 optional parameters and multiple URL-focused sibling tools, the description is incomplete. It lacks return information, which parameters are meaningful, how to interpret failures, and explicit use cases beyond the minimal 'check a URL.'

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 descriptions cover 100% of properties, so the baseline is 3, but the tool description never maps the 9 optional parameters to the action. Several parameters (ref, city, feed, json, path, zone, query) appear unrelated to checking a URL, and with 0 required parameters it is unclear what input is actually needed.

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 clear verb and resource: 'Check whether a URL can be opened.' However, it does not define what 'opened' means (HTTP reachability, DNS lookup, syntactic validity) or how this differs from sibling tools like fetch-status or browser-url-ok.

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 on when to use this tool versus the many URL-related siblings such as browser-url-ok, normalize-url, or fetch-status. The only selection hint is the negative statement 'No browser is launched,' which is insufficient for choosing among similar tools.

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