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

With no annotations, the description carries the behavioral disclosure burden. It does disclose at least one meaningful behavior: no browser is launched. However, it does not explain what 'can be opened' actually entails (URL format check, HTTP request, DNS lookup), whether side effects or network calls occur, or what the return value looks like. The schema parameter descriptions mention discarded inputs, but the tool description itself remains thin.

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 compact and front-loaded: the first sentence states the action, the second clarifies a key behavioral distinction. There is no filler. It could have added a brief note about which parameter to use, but as written it is efficient and easy to parse.

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 optional parameters and no annotations or output schema, yet the description only addresses URL checking. It does not tell the agent which parameter to populate, what the result looks like, or whether a network request is made. The narrow description combined with the broad schema leaves too much to inference, making the definition incomplete for correct invocation.

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 has 100% description coverage, with each parameter individually explained, including which values are discarded. The tool description adds no parameter-level meaning beyond the schema. Since the schema already documents the parameters thoroughly, the baseline score of 3 is appropriate.

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 gives a clear verb and resource: 'Check whether a URL can be opened.' It also adds a useful differentiator, 'No browser is launched,' which separates it from the sibling playwright-url-ok. However, the schema contains 9 unrelated optional parameters, and the description does not clarify that this tool only cares about the url parameter, slightly muddying the overall scope.

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 explicit when-to-use or when-not-to-use guidance. The phrase 'No browser is launched' implies a contrast with playwright-url-ok, but the description does not state conditions for choosing this tool over normalize-url, fetch-status, web-fetch, or other siblings. The usage context is only implicit, not explicit.

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