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 reveal that no browser is launched, but it does not explain how the URL is actually checked, whether a network request is sent, what response or success criterion is used, or what side effects or limitations exist. This is barely enough for an agent to reason about behavior.

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 with no filler. The core purpose is stated first and the key execution detail, 'No browser is launched,' is delivered immediately after. Every word contributes.

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, many of which are unrelated to URL checking (e.g., city, json, query), no annotations, and no output schema. The description does not explain how these parameters interact with the check, what the result looks like, or what 'can be opened' means operationally. An agent is left with significant uncertainty about how to invoke this correctly.

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?

The input schema has 100% description coverage, so the schema already explains each parameter's apparent role. The tool description itself adds no parameter-level meaning. Since the schema carries the load, a 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 uses a specific verb and resource: 'Check whether a URL can be opened.' The additional statement 'No browser is launched' meaningfully distinguishes it from the sibling browser-url-ok, so an agent can separate it from at least one nearby tool. It is not a perfect 5 because 'opened' is still somewhat ambiguous without specifying the mechanism or success criteria.

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 phrase 'No browser is launched' implies this tool is the non-browser alternative to browser-url-ok, but the description never explicitly says when to use this tool instead of others like fetch-status or normalize-url. There is no direct when-to-use guidance or exclusion of alternatives.

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