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

With no annotations, the description carries the full behavioral burden. It discloses only that no browser is launched, but does not explain what 'can be opened' means, whether a network request is made, what the return value looks like, or what side effects may occur.

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 very concise and front-loaded, with no filler. Both sentences earn their place, though the brevity leaves important behavioral details unstated.

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 annotations, and no output schema, so the description is too thin to fully orient an agent. It does not explain the purpose of the non-URL parameters, the success criteria, or the output format.

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 even without additional parameter detail in the description. The description adds no meaningful parameter semantics beyond the word 'URL', and the schema's own 'url' description mentions 'normalize or cite' rather than 'open', creating mild ambiguity.

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 ('Check') and resource ('whether a URL can be opened'). The added 'No browser is launched' distinguishes it from browser-based tools, but 'can be opened' is ambiguous about whether this means URL syntax validity, DNS resolution, or HTTP reachability.

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 implies this is a lightweight URL check suitable when a browser is not needed, but it does not explicitly name alternatives like browser-url-ok or fetch-status, nor does it say when to prefer this tool over them.

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