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

No annotations are provided, so the description must carry the behavioral burden. It discloses that no browser is launched, which is a useful negative behavior, but it fails to explain that many parameters are discarded (e.g., 'city', 'zone', 'query') or that the tool appears to perform shape checks. There's no mention of side effects, auth, or limitations. The description is too thin for a tool with 9 optional parameters.

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 concise — two short sentences — and not bloated. However, it omits crucial context and doesn't structure information logically. It's appropriately sized but under-specified, so it earns a middle score.

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 optional parameters, no required ones, and no output schema, the description should clarify the role of each parameter and what the tool returns. It does neither. The description doesn't explain how the URL is validated, what 'opened' means, or how the other parameters fit in. An agent cannot reliably invoke this tool correctly based on the given information.

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 has 100% coverage with per-parameter descriptions, but those descriptions are confusing and often irrelevant to the stated purpose (e.g., 'city' for weather, 'zone' for timezone). The tool description adds no parameter information, and the schema descriptions themselves contradict the tool's focus on URL checking. Baseline for high coverage is 3, but the contradictory and irrelevant parameter descriptions reduce the value.

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 specific action — 'check whether a URL can be opened' — and adds a key differentiator: 'No browser is launched.' This distinguishes it from browser-launching tools like browser-url-ok, though it doesn't explicitly name alternatives. The verb+resource is clear, but it could be more explicit about why this tool exists vs. siblings.

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 gives no guidance on when to use this tool versus alternatives. It doesn't mention scenarios, exclusions, or contexts where this tool is preferred. With siblings like browser-url-ok, normalize-url, and web-fetch, the agent has no basis for selecting this one.

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