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

With no annotations, the description carries the full transparency burden, but it only reveals a negative fact: no browser is launched. It does not explain whether the tool performs a network request, what 'opened' means, whether it returns a boolean/status, or whether any inputs are actually used beyond the URL, leaving key behavior undisclosed.

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 one tight sentence with no filler and the key caveat ('No browser is launched') is included in the same breath as the main action. 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?

The definition is too sparse for a tool with no output schema, no annotations, nine optional parameters, and many closely related siblings. It does not state the return value, clarify the meaning of 'can be opened,' or explain why the URL parameter is described as 'to normalize or cite' rather than 'to check,' so an agent cannot confidently predict the tool's behavior.

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%, and each of the nine optional parameters has its own description, including discard behavior, so the schema already documents parameter semantics. The tool description adds no parameter information, but the high coverage justifies the baseline score of 3.

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 uses a specific verb and resource ('Check whether a URL can be opened') and adds a meaningful negative constraint ('No browser is launched'), which partially distinguishes it from browser-url-ok. However, 'opened' is left ambiguous—it could mean HTTP reachability, syntactic validity, or a Playwright navigation attempt—so it stops short of a fully unambiguous definition.

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?

There is no statement about when to select this tool over siblings, and no alternative tool is named. The 'No browser is launched' clause is a behavioral caveat, not usage guidance; an agent gets no help deciding between playwright-url-ok, browser-url-ok, fetch-status, or web-fetch.

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