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

With no annotations provided, the description has the full burden of behavioral disclosure. It states that no browser is launched but does not explain what 'can be opened' means (e.g., DNS check, HTTP status check, syntax validation). The schema exposes nine unrelated parameters, many described as 'discarded after the check,' which contradicts the narrow 'URL' focus and is not disclosed. This leaves the tool's actual side effects and scope opaque.

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 succinct, consisting of two short sentences with no filler. It front-loads the core purpose ('Check whether a URL can be opened') before the behavior note. Given the tool's surprisingly broad parameter set, the description may be underspecified, but as far as conciseness the text is efficient.

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?

A nine-parameter tool with no output schema and no annotations requires much more contextual explanation. The description does not state what the tool returns (e.g., a boolean, an error per parameter), how to use the multi-parameter input, or what 'can be opened' practically entails. An agent cannot confidently invoke it for anything beyond the trivial URL-only case.

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 parameters are already documented in detail. The description itself adds no further parameter semantics. It mentions 'URL' but does not clarify how the other eight parameters relate to the URL check or why they are discarded. Baseline of 3 applies because the schema covers the parameter details.

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.' It also adds 'No browser is launched,' which helps distinguish it from browser-launch tools like playwright-url-ok. However, it does not explicitly name sibling tools or conditions for choosing this tool over others, so it lacks full sibling differentiation.

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. The phrase 'No browser is launched' implies a lightweight check, but it never spells out when this tool is preferred, when it is not, or which siblings to choose instead. The agent must infer usage entirely from the name and short description.

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