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

With no annotations present, the description carries the full burden of behavioral disclosure. It adds one useful trait—'No browser is launched'—but does not disclose whether network I/O occurs, whether the operation is read-only, what result is returned, or what 'discarded after the check' means in practice. This is insufficient for a tool with nine parameters and no schema-level safety hints.

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 action comes first, and the negative clarification 'No browser is launched' earns its place by countering the typical Playwright/browser assumption. It is not bloated, though it may be overly sparse for the tool's actual complexity.

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 nine optional parameters, no annotations, no output schema, and several close sibling tools, the description is too thin. It fails to explain return values, network behavior, parameter selection, or how this differs from browser-url-ok and fetch-status. The schema covers parameter names but not the tool-level context an agent needs to invoke it 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 description coverage is 100%, so each parameter is already explained individually. The description adds no parameter-level meaning and its URL-focused framing could make an agent unsure whether city, feed, json, path, zone, and query are relevant to this tool. Still, the schema descriptions are detailed enough to carry the parametric semantics on their own.

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 clear verb and resource: 'Check whether a URL can be opened.' However, 'can be opened' is ambiguous—it could mean syntax validity, network reachability, or rendering—and the description does not distinguish this tool from siblings like browser-url-ok or fetch-status. The nine-parameter schema also includes city, json, zone, query, and other non-URL inputs, which the description does not account for.

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 is given about when to use this tool versus browser-url-ok, fetch-status, normalize-url, or citation. The only hint is 'No browser is launched,' which implicitly rules out browser-rendering use cases but does not state when this tool is the right choice or which alternatives to prefer.

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