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

The description discloses exactly one behavior: no browser is launched. It does not say whether the tool makes network requests, whether it is read-only, what determines 'opened,' or that most parameters are discarded after the check. With no annotations, the side-effect profile is largely unknown, placing the full disclosure burden on the description.

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 short sentences, both carrying essential information: the action and the key behavioral exclusion. No wasted words, and the main purpose is front-loaded.

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 accepts 9 heterogeneous parameters and has a large sibling family, yet the description only addresses URL checking. It omits the output format, success criteria, how the other parameters are handled, and any relationship to fetch-status or playwright-url-ok. This is severely inadequate for an agent to select and invoke the tool 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 already provides descriptions for all parameters (high coverage), so the baseline is 3. The tool description adds no parameter-level semantics beyond the generic phrase 'a URL,' and it does not clarify the role of the other eight parameters.

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 action ('Check whether a URL can be opened') and distinguishes from browser-based checks via 'No browser is launched.' However, it is vague about what 'opened' means (syntax, HTTP reachability, DNS?) and ignores the fact that the schema accepts many non-URL parameters (ref, city, json, path, feed, host), making the described scope narrower than the actual tool.

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 'No browser is launched' sentence implies this is the lightweight alternative to browser-driven tools like playwright-url-ok, but no explicit when/when-not guidance or alternative names are given. An agent must infer when to choose this over fetch-status or normalize-url.

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