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

With no annotations, the description must fully disclose behavior, but it only mentions that no browser is launched. It fails to explain what 'can be opened' means (syntactic check, DNS resolution, HTTP status?), what the tool returns, or why most parameters are discarded after a 'shape check.' The schema descriptions add confusion rather than clarity, so the description provides almost no useful behavioral detail.

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 (two sentences) and front-loads the core action, which is good. However, it is so terse that it omits essential details about the tool's actual behavior and parameter handling. It is not redundant, but it is under-specified to the point of being unhelpful.

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 required fields, no output schema, and no annotations, the description is grossly inadequate. It leaves the agent without any understanding of what the tool does beyond a vague URL check, what outputs to expect, or how the various parameters are used. The definition is incomplete for effective tool selection and invocation.

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, but the parameter descriptions are incongruent with the stated purpose. For example, 'city' is for a weather hint and 'json' is for validation, yet the tool claims to check URL openability. The tool description adds no explanation for these parameters and does not clarify how they relate to the URL check, so it fails to compensate for the schema's disjointed semantics.

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 a constraint ('No browser is launched'), but the input schema includes nine unrelated parameters (e.g., city, json, zone, query) that are described as discarded after shape checks. This mismatch makes the tool's actual purpose ambiguous and misleading—the description does not cover the full scope implied by 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?

No guidance is provided on when to use this tool versus the many siblings (e.g., playwright-url-ok, normalize-url, fetch-status). The 'No browser is launched' hint suggests a lightweight alternative to a browser-based check, but this is not stated explicitly, and no alternatives or conditions are given.

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