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

'No browser is launched' is a genuinely useful behavioral disclosure because the tool name otherwise suggests browser activity. Yet with no annotations present, the description carries the full burden, and it does not state whether the check is network-based, purely syntactic, read-only, or whether any other side effects occur.

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, front-loaded with the primary behavior and followed by the key caveat. There is no filler, repetition, or unnecessary detail.

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 nine optional parameters, no annotations, and no output schema, the description is too thin. It does not explain the return format, what 'can be opened' means, or how to select the correct parameter, leaving important operational details unresolved despite the schema covering parameter names.

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 schema has 100% description coverage, so individual parameters are documented and the baseline is 3. The description itself only mentions 'URL' and adds no guidance about which of the nine parameters to pass, how they relate, or what happens if multiple are supplied.

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 ('Check') on a clear resource ('a URL') and adds the important distinction that no browser is launched, which helps separate it from siblings like playwright-url-ok and web-fetch. It is slightly ambiguous whether 'can be opened' means syntactically valid, reachable, or browser-compatible, so it falls short of a 5.

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 intended use is implied: use this tool to verify whether a URL can be opened without actually launching a browser. However, it gives no explicit when-to-use guidance, no alternatives, and no exclusions, so an agent must infer suitability from the tool name and brief description.

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