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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals one trait ('No browser is launched'), but it does not explain whether the tool actually fetches the URL, performs a shape-only check, what constitutes 'ok', or whether side effects occur. The schema descriptions mention 'discarded after the shape check' for several params, but the main description does not convey this behavior.

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 two short sentences with no wasted words. The core purpose is front-loaded, and the behavioral caveat ('No browser is launched') is placed immediately after, making the text efficient and easy to scan.

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 description is far too short for a tool with 9 parameters, no annotations, and no output schema. It does not explain what 'ok' means, what the return value looks like, or how the multiple input types relate to the stated URL purpose. The schema fills in some gaps, but the overall tool behavior remains ambiguous.

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%, so the baseline is 3. The tool description itself adds no parameter meaning and in fact conflicts with the schema by implying URL-only behavior when the schema includes refs, cities, JSON, timezones, and more. The individual schema descriptions are informative, but the description does not tie them together or indicate which parameter is primary.

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 specific action ('Check whether a URL can be opened') and adds a key behavioral note ('No browser is launched'). However, it is misleadingly narrow: the schema accepts nine different kinds of inputs (git ref, city, JSON, timezone, etc.), so the stated URL-only purpose does not reflect the tool's actual scope. It also does not explicitly distinguish this tool from sibling tools like fetch-status or normalize-url.

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 guidance on when to use this tool versus alternatives such as playwright-url-ok, fetch-status, or normalize-url. The phrase 'No browser is launched' implies a lightweight check, but it never states the conditions under which this tool should be preferred over other URL-related siblings.

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