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

With no annotations, the description bears the full burden of explaining side effects. It discloses that no browser is launched, but it does not mention whether a network request is made, whether any data is fetched or cached, what errors can occur, or whether the operation is read-only.

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 short and front-loaded, and both sentences are relevant. However, it is too terse to be considered well-sized because it omits essential details about which input matters and what the check entails.

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 the 9 optional parameters, no output schema, and no annotations, the description is severely incomplete. It does not explain the role of the unrelated parameters, what the tool returns, how the URL check is performed, or under what conditions it succeeds or fails.

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?

Although the schema description coverage is 100%, the parameter descriptions are confusing and mostly irrelevant to the stated purpose. For example, 'url' is described as 'HTTPS URL to normalize or cite' rather than the URL to check, and fields like 'ref', 'city', 'feed', and 'query' are marked as 'discarded,' which actively misleads an agent about the tool's actual behavior.

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 phrase 'Check whether a URL can be opened' states a broad action and object, but it does not specify which parameter is the URL, what 'opened' means, or how this differs from sibling tools like fetch-status, web-fetch, or playwright-url-ok. The purpose is too vague to guide an agent reliably.

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 guidance about when to prefer this tool over alternatives. The only hint is 'No browser is launched,' which implicitly suggests a lightweight check, but it does not say when to use this versus other URL-related sibling tools.

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