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

With no annotations, the description carries full burden. It discloses one behavior (no browser launch), but fails to explain how the check works (e.g., network request, failure modes, side effects). More critically, the parameter schema includes unrelated items (city, json, path, zone) that seem to contradict the stated purpose, leaving the agent uncertain about the tool's true 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 extremely concise: two short sentences with the primary verb and resource front-loaded and a key behavioral note second. There is no fluff or redundant information, making it highly efficient in structure.

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 9 parameters, no annotations, and no output schema, the description is far too minimal. It doesn't explain what each parameter does in the context of the tool, how results are returned, error behavior, or differentiation from the many sibling tools. An agent cannot confidently and correctly call this tool 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 description coverage is 100%, so a baseline of 3 is warranted. However, the description adds no value in explaining how the 9 parameters relate to the URL-checking purpose. The schema descriptions themselves suggest multiple distinct operations (weather, JSON validation, file path), which do not align with the description's focus and create confusion rather than clarity.

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') and adds a distinguishing behavioral note ('No browser is launched') that hints at a difference from browser-url-ok. However, it doesn't name the sibling or clarify exactly what 'opened' means (e.g., HTTP reachability vs. format validation), leaving some ambiguity.

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 explicit when-to-use guidance or mention of alternatives. The only clue ('No browser is launched') vaguely contrasts with a browser-launching tool, but it doesn't name any sibling or specify conditions under which this tool is preferred over normalize-url, fetch-status, or others.

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