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

With no annotations, the description carries full burden. It only discloses that no browser is launched, but not whether it performs an HTTP request, DNS check, or just shape validation. The schema hints that many parameters are 'discarded after the shape check,' suggesting this may be a shape-only check, but the description does not clarify this 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?

The description is a single, concise sentence with no fluff. It front-loads the core action and the key differentiator (no browser). It is appropriately short for the level of detail provided.

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, no output schema, and no annotations. The description does not explain what the tool returns, how it behaves with different parameters (e.g., does it always check only the 'url' parameter, or also others?), or when to use it. It is under-specified for an agent to call correctly.

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 coverage is 100% with each parameter having a description, so the schema already documents the parameters. The tool description adds no extra meaning to the parameters. Baseline of 3 is appropriate, though the schema descriptions themselves are somewhat odd (e.g., url 'to normalize or cite') and could mislead.

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 tool checks whether a URL can be opened, and explicitly adds 'No browser is launched,' which distinguishes it from the sibling 'browser-url-ok.' However, it doesn't mention the 9 parameters, which are mostly unrelated to URL checking, potentially confusing the agent about the tool's true 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?

No guidance on when to use this tool versus alternatives like browser-url-ok, normalize-url, or web-fetch. The 'No browser is launched' line implies a lighter-weight check, but it doesn't explicitly say when to prefer this over siblings.

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