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

The behavior is opaque: 'can be opened' is undefined—does it perform a network request, check syntax, or validate DNS? The parameter list includes unrelated fields (city, zone, query) with descriptions mentioning 'discarded', suggesting a generic shape checker, but the tool description does not clarify this. Without annotations, the description fails to convey actual 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 remarkably concise—two short sentences—with no fluff or redundancy. It front-loads the core purpose and adds a key differentiator in the second sentence.

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?

Given the tool's 9-parameter schema and no output schema, the description is incomplete. It fails to explain how the parameters relate to the tool's purpose, what 'can be opened' means operationally, or what the return value indicates. This leaves significant gaps for an agent.

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 description coverage is 100%, so the baseline is 3. However, the tool description does not add any meaning beyond the schema's sometimes confusing parameter descriptions, nor does it explain the relevance of parameters like city or zone to URL checking.

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's purpose: 'Check whether a URL can be opened.' It uses a specific verb and resource, and the additional clause 'No browser is launched' differentiates it from browser-based tools like playwright-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?

The description implies a lightweight check by noting no browser is launched, but it does not explicitly state when to use this tool over alternatives such as fetch-status or normalize-url. No comparative guidance is provided.

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