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 does disclose an important trait: no browser is launched. But it does not explain how the check is performed, whether a network request is made, or what failure/timeout behavior looks like. This is partial transparency, not complete.

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, front-loaded with the primary purpose, and contains no fluff. Every sentence earns its place. It is appropriately concise, though it leaves out behavioral and output details that would be covered under other dimensions.

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?

Given no output schema, no annotations, nine optional parameters, and a large sibling list, this description is too thin. It does not state what the tool returns, what 'ok' means, or which parameters actually influence the result. The schema hints that many parameters are discarded, but the description itself does not provide enough for confident 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%, with each parameter already described individually, including notes like 'discarded after the check.' The tool description adds no parameter-level meaning beyond what the schema already provides, so the baseline score of 3 is appropriate.

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 and resource: 'Check whether a URL can be opened.' The second sentence, 'No browser is launched,' helps differentiate it from browser-launching siblings like browser-url-ok. However, 'can be opened' is left ambiguous—it does not clarify whether this is a syntax check, DNS check, or HTTP reachability check.

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?

Usage context is only implied. 'No browser is launched' suggests this is a lightweight alternative to a real browser-based check, but the description never names alternatives or states when to prefer this tool over siblings like browser-url-ok or fetch-status. There is no explicit when-to-use or when-not-to-use guidance.

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