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

There are no annotations, so the description carries the disclosure burden. It provides one useful behavioral fact: no browser is launched. However, it does not disclose whether a network request is made, what 'can be opened' means in practice, or what the return value looks like, leaving the tool's runtime behavior only partially transparent.

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. 'Check whether a URL can be opened' states the core purpose, and 'No browser is launched' adds essential differentiation in just five words.

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?

For a simple read-only check tool, the description is largely usable: an agent can infer it takes a URL and returns whether it is openable. But without an output schema or annotations, the exact success criteria and return format are unspecified, and the large set of optional schema parameters is not reconciled with the stated purpose, so the description is not fully complete.

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 each of the nine optional parameters already has an individual description, warranting the baseline score of 3. The tool description adds no per-parameter guidance, but the schema carries the parameter semantics; ambiguity about which parameter to pass for the URL check is mostly resolved by the `url` property and the tool name.

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 action and resource: 'Check whether a URL can be opened.' It also adds a distinguishing behavioral detail, 'No browser is launched,' which helps separate it from sibling tools like browser-url-ok. However, 'opened' is somewhat ambiguous—it could mean HTTP reachability, DNS resolution, or renderability—so it is not perfectly explicit.

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 no-browser note implies this is a lightweight URL check and should not be used when actual browser rendering is required. Still, the description never names alternatives such as browser-url-ok, web-fetch, or fetch-status, and it does not state explicit conditions for when to prefer this tool over them.

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