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. It only mentions that no browser is launched, but it does not explain what 'opened' means (e.g., HTTP status check, reachability), what side effects might occur, why it accepts nine disparate parameters that are mostly discarded, or what the return format is. The description is too sparse to convey the tool's true 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 extremely concise, consisting of two short sentences with no filler. It front-loads the core purpose and the key differentiator. There is no wasted text, so it earns a high score for conciseness, even though it sacrifices depth.

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 tool has nine optional parameters, no output schema, and no annotations, yet the description provides only a minimal statement of purpose. It fails to explain why the diverse parameters exist (e.g., city, zone, json) or how they relate to URL checking, nor does it describe the output or error behavior. For a tool of this apparent complexity, 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?

The input schema has 100% coverage, with each parameter individually described (e.g., 'discarded after the shape check'). The tool description adds no additional parameter information, so it does not go beyond the schema. Baseline of 3 is appropriate because the schema already documents the parameters adequately for invocation.

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 verb ('Check') and a clear resource ('whether a URL can be opened'), and it adds the key differentiator 'No browser is launched,' which distinguishes it from browser-based siblings like playwright-url-ok. However, it does not explicitly name the alternative, so the differentiation is implicit rather than explicit.

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 description provides no guidance on when to use this tool versus its siblings. It only states what it does and the fact that no browser is launched, which hints at a choice but does not offer explicit conditions, alternatives, or exclusions. An agent would have to infer when this is preferable.

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