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

With no annotations, the description carries the full burden. It only says 'No browser is launched,' which clarifies what it doesn't do, but fails to disclose what it actually does—does it perform a network request, validate syntax, or something else? The presence of unrelated parameters (city, json, path) suggests multiple behaviors that are entirely unexplained, effectively contradicting the URL-only framing.

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 short (two sentences), but this is under-specification, not effective concision. It omits critical context about parameters, behavior, and usage. The 'No browser is launched' clarification is helpful but insufficient to compensate for the lack of essential information.

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, and no annotations, the description is grossly incomplete. It does not explain what the tool returns, how parameters interact, or when to use it. An agent cannot confidently invoke this tool correctly based on the description alone.

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 descriptions are 100% covered, so the baseline is 3, but the tool description adds no linkage between parameters and the stated purpose. It does not explain why a 'city' or 'json' parameter is relevant to checking a URL, leaving the agent confused about how to select or interpret parameters. This lowers the score below baseline.

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 verb and resource ('Check whether a URL can be opened') but leaves 'opened' ambiguous—does it mean HTTP status, reachability, or format? It does not differentiate from siblings like fetch-status or normalize-url. The tool name and many unrelated parameters (city, json, path, zone) suggest a broader purpose, making the stated purpose misleading.

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 on when to use this tool vs. the many URL-related siblings (fetch-status, web-fetch, normalize-url, etc.). No mention of prerequisites, exclusions, or conditions that would select this tool over others.

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