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

There are no annotations, so the description carries the full burden. It does disclose the key behavioral trait that no browser is launched, which is useful and non-obvious from the name. However, it does not explain what 'can be opened' means operationally (e.g., HTTP status, timeout, network behavior) or reveal that most input parameters are 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 concise sentences with no wasted words. The core purpose is front-loaded, and the key behavioral caveat follows immediately. This is appropriately scoped for the tool's apparent simplicity.

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?

Despite a clear purpose sentence, the tool exposes seven heterogeneous parameters (ref, url, city, feed, host, json, path) and has no output schema or annotations. The description does not clarify which parameter should be passed for the URL check, what the return value looks like, or why city and json are accepted. An agent cannot confidently determine invocation requirements from this definition alone.

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 description itself adds no parameter information, but the input schema already provides detailed descriptions for each parameter, many explicitly noting they are 'discarded' after the check. With schema coverage effectively high, the baseline of 3 applies; the description does not add meaning beyond the schema.

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.' It also distinguishes itself from sibling tools like browser-url-ok by explicitly stating 'No browser is launched,' which clarifies that this is a lightweight URL reachability check rather than a full browser operation.

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 statement 'No browser is launched' implies this tool is appropriate when a simple URL-open check is needed without browser rendering, but it does not explicitly name alternatives or state when to use this instead of browser-url-ok, fetch-status, or web-fetch. Usage context is implied rather than directly instructed.

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