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

With no annotations present, the description must disclose behavioral traits itself. It does provide one useful disclosure, that no browser is launched, but it does not state whether a network request is made, whether the URL is merely parsed or actually fetched, what side effects occur, or how the discarded parameters behave at the tool level. The schema's 'discarded' notes help but are structured fields, not behavior description, and no auth or rate-limit context is given.

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 carry the core purpose and a critical behavioral caveat without filler. Every word earns its place, and the leading sentence front-loads the main action.

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, a vague purpose, and no output schema, describing only 'Check whether a URL can be opened' is incomplete. The agent is not told what result to expect, how to configure the relevant parameter, or when this is a better choice than the many URL/checking siblings; the single sentence is not enough to call this tool confidently.

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 all nine parameters are already documented, including the 'discarded' behavior for most of them. The description adds no parameter-level meaning, but per the rubric this is acceptable when the schema covers the full contract; it neither helps nor harms beyond the baseline.

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 verb and resource ('Check whether a URL can be opened') and adds a meaningful constraint ('No browser is launched'), which partially separates it from browser-based siblings like browser-url-ok. However, 'opened' is ambiguous (HTTP reachability vs URL parsing vs tool smoke-test), and the schema accepts nine unrelated optional parameters (city, zone, json, query, etc.) with 'discarded' notes that the description never reconciles with the stated URL-checking purpose.

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?

There is no guidance on when this tool should be used instead of browser-url-ok, web-fetch, fetch-status, or the other URL/checking siblings. The description does not mention alternatives, prerequisites, or conditions that would select this tool, leaving the agent to infer the intended niche from the name alone.

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