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

No annotations are provided, so the description carries the full burden. It discloses that no browser is launched, but it does not mention whether an HTTP request is made, whether the operation is read-only, what side effects occur, or what the return value looks like. The behavior is largely unspecified.

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 sentence with no waste, but it is under-specified rather than concisely complete. It omits essential information about return values, parameter usage, and relationship to siblings, so the brevity is a deficiency, not a virtue.

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?

With 9 parameters, no output schema, no annotations, and a vague description, the tool is critically incomplete. An agent cannot determine what the tool returns, how to interpret 'opened,' or why the diverse parameters are included. The description fails to provide enough context 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?

Schema coverage is 100% with per-parameter descriptions, so the baseline is 3. However, the tool description claims it checks whether a URL can be opened, while the schema includes many non-URL parameters (city, feed, json, path, zone, query) that are all described as 'discarded after' a shape check. The tool description provides no mapping between these parameters and the stated purpose, creating confusion about which parameter is the actual URL and why the others exist.

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 action (check whether a URL can be opened) and explicitly differentiates from browser-url-ok via 'No browser is launched.' However, 'opened' is ambiguous (HTTP status? reachability? redirects?), and it does not name any sibling tool, relying on the negative phrase alone.

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 guidance on when to use this tool versus alternatives like fetch-status, normalize-url, or browser-url-ok. The only hint is the negative statement 'No browser is launched,' which implies a use case but never states it directly or lists alternatives.

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