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

With no annotations, the description must explain side effects and data access; it only says 'without WHOIS or data' but does not state whether network/DNS lookup occurs, what is returned, or that unrelated params are discarded. Several param descriptions mention 'discarded after the shape check,' which contradicts the 'split' behavior in 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?

The description is brief and front-loaded, but brevity comes at the cost of necessary detail; it reads more like a terse hint than a usable specification.

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 has 9 optional parameters, no required parameters, and no output schema. The description fails to specify what input should be provided, how the parameters relate, or what result shape to expect, so an agent cannot confidently invoke it.

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?

Although every parameter has a textual description, they are largely unrelated to splitting a hostname (url, city, feed, json, path, zone, query) and the descriptions suggest shape-check/discard semantics rather than hostname label splitting. The only relevant-looking parameter is 'host', but its description 'Public hostname' is too thin to clarify usage.

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 action and object ('Split a hostname into labels'), but the phrase 'without WHOIS or data' is ambiguous and the input schema exposes nine unrelated optional fields, with no dedicated hostname parameter except 'host'. This makes the tool's actual purpose unclear and poorly differentiated from sibling shape/URL tools.

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 use this tool versus alternatives like normalize-url, browser-url-ok, or other shape checkers. The only hint is the negative 'without WHOIS or data', which is not enough to route an agent reliably.

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