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

No annotations are provided, so the description alone must disclose side effects and behavior. It does state that no browser is launched, which is useful, but it fails to explain what 'can be opened' means operationally: whether a network request is made, what is checked, whether data is fetched, or whether any state changes occur. Given the tool has nine parameters and several 'discarded after' behaviors, the description is too thin.

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, front-loaded sentence with no filler. Both statements are meaningful: the tool's action and a key behavioral constraint. This is concise without sacrificing clarity.

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?

While the schema covers parameters and the description gives the primary purpose, the tool has no output schema and no annotations. It does not describe expected outcomes, failure conditions, or how to interpret the result. The large set of auxiliary parameters also makes the overall context incomplete without more explanation about why they are accepted or how they influence the check.

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 the schema already documents every parameter. The description adds minimal value by connecting the 'url' parameter to the main purpose, but it does not explain the roles of the other eight parameters or how they relate to the URL check. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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?

Description states a specific verb ('Check') and resource ('whether a URL can be opened'), and adds a distinguishing behavioral note ('No browser is launched') that separates it from sibling tools like browser-url-ok. This clearly identifies the tool's core function.

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 implies a lightweight check that does not launch a browser, which offers some context for when to choose it over heavier browser-based tools. However, it does not explicitly state when to use this tool versus alternatives such as browser-url-ok, fetch-status, or normalize-url, leaving usage guidance mostly implicit.

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