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

With no annotations, the description must disclose all relevant behavior. It clarifies that no WHOIS/ownership lookup happens, which is useful, but it fails to mention that most parameters are 'discarded after the shape check' (as stated only in the schema), that the tool appears read-only, or what happens with invalid inputs. The description covers only the hostname case, leaving the behavior for other fields undefined.

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, which is concise, but it is under-specified to the point of being misleading. It does not front-load the tool's broad applicability (9 parameters) and wastes its brevity on a single use case, so it does not 'earn its place' despite the short length.

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 output schema, and no annotations, the description is grossly incomplete. It does not explain return values, error behavior, or how the shape check applies to non-hostname inputs, and it provides no context for an agent to safely call it with the right parameter. The complexity demands far more than what is offered.

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%, with each of the 9 parameters individually documented. However, the tool description adds no meaning beyond the hostname focus and does not explain how parameters relate or which one to use. It neither helps nor hurts the schema semantics, so the baseline of 3 is appropriate.

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 (split hostname into labels) but the schema accepts 9 unrelated parameters (ref, url, city, feed, json, path, zone, query), implying a much broader 'shape check' purpose. This is misleading about the tool's actual scope and does not clearly distinguish it from sibling shape tools like github-repo-shape or figma-url-shape beyond a nod to 'without WHOIS or ownership data'.

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 is given on when to choose this tool over its many siblings (e.g., normalize-url, file-path-ok, validate-json). The phrase 'without WHOIS or ownership data' hints at a lightweight check but does not name alternatives or specify conditions for selection, leaving an agent to guess which parameter should be populated.

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