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

With no annotations, the description carries the behavioral burden and does disclose one important trait: no browser is launched. However, it does not say whether a network request is made, what side effects may occur, what the return value looks like, or how failures are reported, leaving meaningful gaps.

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 just two sentences, front-loads the purpose, and contains no filler. It is concise and scannable, though it could earn a 5 by packing in more decision-useful context such as return behavior or sibling differentiation.

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?

For a tool with nine optional parameters, no annotations, and no output schema, two sentences are insufficient. The description does not explain the meaning of 'opened,' the return type, the role of the url parameter relative to the discarded ones, or how to choose this tool among the many URL/network siblings.

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: each optional parameter has its own description, most noting that values are discarded. The tool description adds no parameter-level meaning and does not clarify which parameters actually matter for the URL-open check, so it neither improves nor damages the schema's parameter guidance.

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 names a specific action and resource: 'Check whether a URL can be opened.' It also adds a distinctive caveat, 'No browser is launched,' which helps separate this from browser-based sibling tools. It stops short of a 5 because 'can be opened' is ambiguous: it could mean URL syntax validity, network reachability, or an HTTP success 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?

The first sentence implies the use case: call this when you need a URL-open check. The 'No browser is launched' line hints that this is the lightweight/non-browser option among URL tools, but it never names alternatives like browser-url-ok or fetch-status, nor does it state when not to use this tool.

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