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

With no annotations provided, the description carries the full behavioral burden. It usefully discloses that no browser is launched, which prevents a natural assumption based on the tool name. But it does not explain whether a network request is made, what 'opened' means, what the result looks like, or whether there are any side effects or access constraints.

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 definition is two short sentences with no filler. The core purpose is front-loaded, and the behavioral caveat 'No browser is launched' earns its place by clarifying a likely misconception. It is as compact as possible for what it conveys.

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 9 optional parameters, no annotations, no output schema, and many similar siblings, a single sentence is insufficient. Missing details include the return type, the precise meaning of an 'openable' URL, how the other parameters relate to the check, and any network or safety behavior; only the no-browser fact is provided.

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 coverage is 100%, so the baseline is 3, but the description provides no guidance for choosing among the 9 optional parameters. The schema's url description ('HTTPS URL to normalize or cite') conflicts with the tool's stated purpose of checking whether a URL can be opened, and unrelated parameters such as city, json, and timezone are unexplained, making it unclear which parameter actually drives the check.

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 action ('Check whether a URL can be opened') and adds a key behavioral distinction ('No browser is launched'), which separates it from browser-launching tools like playwright-url-ok. However, 'can be opened' is ambiguous—syntax validation, HTTP reachability, and renderability are all plausible—and no sibling is explicitly named, so it stops short of a 5.

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 when to use the tool: when a caller wants an openability check without launching a browser. It does not provide explicit when-to-use versus alternatives such as fetch-status, web-fetch, or playwright-url-ok, nor does it state any exclusions or fallback conditions.

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