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

With no annotations, the description carries the full burden of behavioral disclosure, but it only says 'No browser is launched.' It does not explain whether the tool makes network requests, performs a purely syntactic shape check, has side effects, or what it returns. The schema's 'discarded after the shape check' and 'no disk access' notes add some behavior, but the description itself is thin.

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 concise and front-loaded with the primary action, and both sentences earn their place. However, it is under-specified for the tool's actual complexity: two short sentences do not adequately describe a nine-parameter tool.

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?

This is a complex tool with nine optional parameters, no annotations, and no output schema. The description fails to explain how the parameters relate, which one to use for a given intent, what 'opened' means, or what the result looks like. The schema provides some context, but the description is far from complete.

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 description adds no parameter-level meaning beyond the schema, and it actually obscures the relevance of the non-URL parameters. The per-parameter schema descriptions are doing the real semantic work.

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 behavioral note ('No browser is launched'), but the input schema exposes eight other unrelated parameters such as city, zone, query, json, and path. An agent cannot tell whether this tool checks URLs only, validates many input shapes, or does something else entirely, so the stated purpose is misleading relative to the schema.

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 sibling tools like normalize-url, fetch-status, playwright-url-ok, or domain-shape. 'No browser is launched' hints that this is a non-browser check, but no alternatives or selection conditions are provided.

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