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

No annotations exist, so the description carries the burden. It states a non-destructive action (splitting) and explicitly excludes WHOIS/ownership data, but does not disclose any error behaviors, output format, or side effects. The lack of detail about edge cases (e.g., invalid hostnames) reduces transparency.

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, concise sentence that conveys the core functionality without extraneous wording. It is well-structured and front-loaded with the verb and resource.

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 the simple nature of the tool, the description omits crucial context: it does not explain how parameters map to inputs, what output to expect, or how it differs from related tools beyond a single qualifier. The mismatched schema amplifies the incompleteness, leaving an agent unable to correctly invoke the tool.

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 parameter descriptions are generic and mismatched to the tool's purpose. For instance, 'url' says 'normalize or cite,' 'json' says 'validate,' and 'zone' says 'IANA timezone name,' none of which relate to splitting hostnames. The description does not explain how to use these parameters, and the 'host' parameter is not explicitly connected to the action.

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 clearly states the action ('Split a hostname into labels') and adds a qualifier ('without WHOIS or ownership data'), distinguishing it from sibling tools like normalize-url or iana-zones. However, it does not explicitly identify which parameter to use as the hostname input, leaving slight ambiguity.

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 provided on when to use this tool versus alternatives such as normalize-url or inspect-robots. There is no mention of scenarios where splitting hostnames is preferable or how this tool fits into a workflow.

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