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

The statement 'without WHOIS or data' discloses that the tool does not perform network or data-fetching operations, implying a pure computation. With no annotations provided, this partial behavioral disclosure is helpful, though it does not mention edge cases or error behavior.

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, brief sentence that is direct and to the point. The phrase 'or data' is somewhat vague but does not significantly detract from the overall clarity.

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 mismatched schema, the description fails to explain which parameter should be used for the hostname or how the tool relates to the other parameters. A user would be uncertain whether to pass 'host', 'url', or something else, making the tool contextually incomplete.

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 schema parameters (url, host, json, timezone) and their descriptions are clearly mismatched with the tool's purpose. For example, 'json' is described as 'JSON text to validate' and 'timezone' as 'IANA timezone name', which are irrelevant to splitting a hostname. The description does not clarify how to pass the hostname, and the parameter descriptions appear copy-pasted from unrelated sibling tools.

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 the resource (hostname). It also differentiates from sibling tools by explicitly excluding WHOIS and data retrieval, which clarifies its scope.

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?

The description implies when to use the tool (when you need to split a hostname) and provides a negative condition ('without WHOIS or data') to set expectations. However, it does not explicitly name alternative tools for WHOIS or data-related tasks, leaving some inference required.

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