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

With no annotations, the description must carry the behavioral burden. It does disclose a key non-effect ('No browser is launched'), but it does not say whether the tool makes a network request, what 'can be opened' means, or how the seven non-URL schema parameters are treated beyond the schema's own discard notes.

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?

Two short sentences with no filler. The key purpose is stated first and the important non-effect ('No browser is launched') is immediately after. Every word earns its place.

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 tool with seven parameters, no annotations, and no output schema, this one-sentence description is inadequate. It explains only the core intent and one limitation, while leaving the multiple parameters, return shape, and side effects unexplained.

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?

All seven parameters have schema descriptions, so the baseline is 3, but the tool description does not build on them and actually conflicts with the schema: it is URL-only while the schema exposes ref, city, feed, json, and path. The description neither reconciles those parameters nor says they are ignored.

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 useful negative ('No browser is launched') that distinguishes it from browser-launching siblings. It stops short of 5 because it doesn't name the sibling it differs from or clarify what 'opened' means beyond not launching a browser.

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 prefer this tool over alternatives such as playwright-url-ok, web-fetch, or normalize-url. The 'No browser is launched' clause implies a lightweight check, but that is not developed into an explicit when-to-use/when-not-to-use statement.

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