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

With no annotations provided, the description carries the full burden of disclosing behavior. It states a HEAD request and 'return status only,' but does not explain side effects, permissions, rate limits, or what happens with the other parameter types (e.g., whether they trigger network calls or are purely local checks). The schema parameter descriptions hint at 'discarded after the shape check,' implying no persistent effect, but this is not consolidated in the tool 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?

The description is a single sentence with no filler, which is concise and front-loaded. However, it is under-specified to the point of being cryptic—it omits the tool's broader applicability and leaves the agent uncertain about the other 8 parameters. Conciseness is achieved at the cost of clarity, so it earns a middle score.

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?

Given 9 optional parameters, no output schema, and no annotations, the description is severely incomplete. It explains only one use case (URL status) and ignores the rest, leaving the agent without enough context to correctly invoke the tool for non-URL inputs. The return value is not described beyond 'status only,' and error conditions are absent.

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 the baseline is 3 even with no parameter information in the description. The tool description adds no parameter-specific detail; it only mentions URL. The schema descriptions are somewhat vague (e.g., 'discarded after the shape check') but do exist, so the description does not need to compensate heavily. It neither improves nor detracts from 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?

States a clear action (HEAD a public URL and return status) for a specific resource, but the description only mentions the URL parameter while the schema exposes 8 other parameters (ref, city, feed, host, json, path, zone, query) that are not addressed. This narrow framing makes the tool's full scope ambiguous and does not differentiate it from siblings like web-fetch or normalize-url.

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?

No guidance on when to use this tool versus alternatives. Sibling tools like browser-url-ok, playwright-url-ok, and web-fetch overlap in URL handling, but the description gives no conditions, exclusions, or alternative recommendations. The agent is left to infer usage 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.