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

The only behavioral disclosure is 'No browser is launched,' which clarifies a non-browser approach. However, it does not mention whether the tool makes network requests, follows redirects, checks responses, or has any side effects or rate limits. With no annotations provided, this sparse disclosure leaves most behavior unknown.

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, consisting of two short sentences that convey the core action and a key limitation. It avoids unnecessary detail and is efficiently structured. However, it lacks examples or structured breakdown that could enhance clarity without bloating.

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?

The description is highly incomplete given the nine parameters and lack of output schema. It does not explain how the parameters relate to checking a URL (e.g., what 'ref', 'city', 'feed', etc., mean for this action), what constitutes 'can be opened' (e.g., HTTP 200 vs. any response), or what the return value indicates. Critical operational context is missing, making the tool effectively unusable 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?

The parameter descriptions are entirely mismatched with the tool's purpose. For example, 'ref' is described as 'Git ref name; discarded after the shape check' and 'city' as 'City name for a public weather hint; discarded after the call.' These are irrelevant placeholders that would mislead an agent. The 'url' parameter description ('HTTPS URL to normalize or cite') is also vague and inconsistent with 'check whether a URL can be opened.'

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 clearly states the action ('Check whether a URL can be opened') and the resource (URL). It is specific but does not differentiate from similar sibling tools like browser-url-ok or fetch-status, which could also check URL accessibility. The phrase 'No browser is launched' adds a slight differentiator but is more about behavior than purpose.

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 indication of when to use this tool instead of alternatives. It lacks any comparison to sibling tools or conditions that would guide selection. An agent would have to guess whether to use this for a quick status check versus a full browser call.

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