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

The only disclosed behavioral trait is that no browser is launched, which is useful but insufficient. With no annotations present, the description should also clarify whether the tool performs a network request, has side effects, or returns a yes/no answer. Without this, an agent cannot fully anticipate the tool's behavior.

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?

Two short, front-loaded sentences with no redundant wording. The key differentiator, 'No browser is launched', is placed immediately after the main statement and earns its place.

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 seven heterogeneous parameters, no annotations, and no output schema, this description is too thin. It omits the return value, the nature of the check, and any usage conditions. The schema fills in parameter meanings, but the overall contract for calling the tool remains incomplete.

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 input schema provides descriptions for all seven parameters, so schema coverage is 100% and the baseline is 3. The description itself adds no parameter-specific meaning, and its single mention of 'URL' does not clarify why parameters such as city, json, or ref are accepted.

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 specific action and object: 'Check whether a URL can be opened.' The addition of 'No browser is launched' helps distinguish it from browser-based siblings such as playwright-url-ok. However, 'can be opened' remains slightly ambiguous about whether this is a network reachability check, a format/parse check, or something else.

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 choose this tool over alternatives like fetch-status, playwright-url-ok, or normalize-url. 'No browser is launched' reads as a behavioral note rather than an explicit usage condition, so an agent is left to infer the appropriate context.

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