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

The description does disclose a useful behavioral boundary: it only splits labels and deliberately excludes WHOIS or ownership data. Because annotations are absent and there is no output schema, it still fails to disclose what the tool returns, whether it performs any network access, or what happens when inputs are invalid.

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 front-loaded sentence with no filler or repeated schema information. Every word adds meaning: the verb, the resource, and the explicit exclusion of WHOIS/ownership data.

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 a seven-property input schema, no output schema, and no annotations, this one-sentence description leaves too much unstated. An agent cannot tell whether host is required, what the output shape looks like, or what role the other schema fields play, so the tool is not fully specified for reliable invocation.

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?

All seven parameters already have descriptions in the input schema, so the baseline is 3. The tool description reinforces that 'host' represents the hostname to split, but it adds no meaning for the other six parameters (ref, url, city, feed, json, path) and does not clarify whether they are relevant to this tool.

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 operation—'Split a hostname into labels'—with a clear resource and a negative scope ('without WHOIS or ownership data') that prevents confusion with ownership-enrichment tools. It does not fully distinguish itself from sibling shape tools, and the one-line purpose does not explain the broad input schema that includes city, json, path, and other unrelated-looking fields.

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 the intended use case: an agent should call this when it needs hostname label splitting and does not need WHOIS/ownership enrichment. However, it offers no explicit guidance on when not to use it, no alternatives, and no comparison to siblings like normalize-url, web-fetch, or other shape tools.

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