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

With no annotations available, the description carries the full burden of behavioral disclosure. It only states that no browser is launched, but does not say whether a network request is made, whether the check is read-only, how results are returned, or what 'opened' means. The schema's 'discarded' notes hint at non-persistence, but the description itself is insufficient.

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 genuinely concise and front-loads the main action, with no wasted words. However, the brevity is achieved by under-specification: for a tool with seven parameters and multiple implied behaviors, two sentences are not an appropriately sized description.

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 complex seven-parameter schema, no annotations, and no output schema, this description is severely incomplete. It does not explain the return value, the meaning of 'opened,' how the other parameters relate, or any side effects. An agent cannot confidently call this tool correctly 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 input schema provides 100% description coverage, so the baseline is 3, but the tool description fails to add context and actually conflicts with the schema: the `url` parameter is described as 'HTTPS URL to normalize or cite' while the tool description says it checks whether a URL can be opened. The description also gives no explanation for the unrelated parameters (ref, city, feed, host, json, path), increasing confusion.

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 key modifier ('No browser is launched'), which lightly distinguishes it from browser-launching siblings. However, 'can be opened' is ambiguous—it could mean syntactic validity, HTTP reachability, or something else—and the description ignores the seven input parameters, leaving the tool's real scope unclear.

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?

No guidance is given about when to choose this tool over sibling tools such as normalize-url, fetch-status, web-fetch, or browser-url-ok. The only implicit hint is the negative 'No browser is launched,' which suggests using it when avoiding a browser, but it never spells out the selection criteria or context.

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