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

With no annotations, the description itself must carry behavioral disclosure. It does disclose a key trait: no browser is launched, which sets expectations about side effects. However, it omits whether a network request is made, what 'opened' means (e.g., HTTP 200 vs URL parse), and whether any data is persisted or discarded.

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?

Two short sentences, with the core purpose first and the crucial caveat second. No filler or redundant information.

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 description is too thin for a tool with 9 optional parameters, no output schema, and no annotations. It does not describe return values, what happens when multiple parameters are provided, or how to pick among the many accepted inputs; the schema descriptions partially compensate, but the overall calling context remains underspecified.

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 every parameter already has a semantic description. The tool description adds no parameter-level information beyond the schema, 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 operation ('Check whether a URL can be opened') and adds a meaningful mechanism note ('No browser is launched'). This makes the tool's primary purpose clear, though it does not explicitly differentiate it from sibling tools like browser-url-ok or fetch-status.

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 about when to choose this tool over browser-url-ok, normalize-url, or fetch-status. The 'No browser is launched' note hints at a non-browser check but never states the recommended conditions or alternatives.

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