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

With no annotations, the description must carry the full burden of behavioral disclosure. It conveys the basic parse operation and one exclusion, but it does not describe the output format, failure behavior, or whether any network or external lookups are performed beyond the stated absence of WHOIS data.

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, focused sentence with no wasted words. The core behavior and a key limitation are stated upfront.

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 definition is too thin for a tool with no annotations, no output schema, and four optional parameters. It does not explain how the parameters relate to the tool's purpose, what result an agent should expect, or why parameters like json and zone are present.

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 has 100% description coverage, so each parameter is individually documented. However, the tool description does not clarify how 'hostname' maps to the host parameter or whether url is also accepted, leaving some ambiguity among the four optional parameters.

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 and resource: it splits a hostname into labels and explicitly excludes WHOIS or ownership data. This makes the core purpose clear, but it does not distinguish the tool from close siblings such as normalize-url, which also works with hostnames and URLs.

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 gives no guidance on when to use this tool versus alternatives like normalize-url, validate-json, or timezone. The only contextual hint is the negative clause 'without WHOIS or ownership data', which says what the tool does not provide rather than when an agent should choose it.

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