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

With no annotations, the description carries the behavioral disclosure burden. It usefully discloses that WHOIS/ownership data is not included. But it does not describe output format, error handling for invalid hostnames, or the fact that most of the declared parameters appear to be discarded or irrelevant to this tool.

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?

One tight sentence with no filler. The verb and object are front-loaded, and the 'without WHOIS or ownership data' qualifier adds useful scope without bloating the text.

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?

Without annotations or an output schema, the description is too thin. It does not state what the returned labels look like, how invalid hostnames are handled, or which parameter should actually be populated given the large optional input schema. An agent could guess 'host', but the definition leaves important invocation details unclear.

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%, so the baseline is 3. The description adds no param-specific meaning beyond the word 'hostname', and while it implies 'host' should be used, it leaves the purpose of the other eight params unexplained.

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 a hostname into labels') and a clear boundary ('without WHOIS or ownership data'). It is more specific than a vague phrase, but it does not name sibling tools to explicitly differentiate them.

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?

It implies when to use the tool: when you need syntactic domain labels and not WHOIS or ownership enrichment. However, it does not explicitly say when to prefer this over sibling tools like normalize-url or browser-url-ok, nor does it clarify that only the 'host' parameter is relevant among the nine optional schema fields.

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