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

The description discloses that 'No browser is launched', which is a useful side-effect note, but it omits other likely behaviors such as whether a network request is made, what errors might occur, or whether the check is local syntax-only. With no annotations, the burden falls on the description, and it only partially covers it.

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 extremely concise—two short sentences with no filler, redundant wording, or unnecessary detail. It gets to the point immediately and avoids fluff, making it 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 description lacks essential contextual information: it does not specify the return value or output format, which parameters are actually used versus discarded, or how it differs from closely related sibling tools. With 9 parameters and no output schema, the agent cannot fully anticipate the tool's behavior or success criteria.

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 schema provides descriptions for all 9 parameters, but many appear unrelated to the stated purpose (e.g., 'city' for weather, 'zone' for timezone, 'query' for search length). The descriptions note that several are 'discarded' after a shape check, yet the description does not explain why these parameters are accepted or how they relate to URL checking. This creates confusion rather than clarity.

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 the tool 'Check whether a URL can be opened', which gives a clear action and resource, but leaves ambiguity about what 'can be opened' means (e.g., HTTP status, DNS resolution, rendering). It does not differentiate itself from sibling tools like fetch-status or playwright-url-ok, so the purpose is only moderately clear.

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?

The description provides no guidance on when to use this tool over the many similar siblings (fetch-status, normalize-url, playwright-url-ok, web-fetch). There is no mention of conditions, alternatives, or scenarios, leaving the agent to guess selection criteria.

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