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

No annotations exist, so the description must carry the safety/behavior burden. It does disclose one meaningful trait—no WHOIS or ownership lookup—but does not explicitly state that it is a pure/no-network read operation or that unrelated input fields are discarded.

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?

A single 9-word sentence that front-loads the action and object, with no filler. It is concise, though the same brevity causes the missing usage and parameter context.

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?

For a tool with no output schema, no annotations, 9 optional params, and many sibling shape/URL tools, this is not complete. There is no return-format note, no invalid-input behavior, and no statement that other params are ignored.

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 9 parameters are already described in the schema (100% coverage), so the baseline is 3. The description adds no param-specific guidance and does not nominate `host` as the only relevant parameter, leaving the wide optional surface ambiguous, but the schema itself is informative.

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 names a specific verb ('split'), a concrete resource ('hostname'), and the output ('labels'), and adds an explicit scope constraint ('without WHOIS or ownership data'). This is enough to distinguish it from ownership-enrichment tools, though not from other shape-check siblings.

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 when-to-use guidance and names no alternatives. With 27 sibling tools like normalize-url, github-repo-shape, and wiki-title-ok, an agent is left to infer the correct choice from the name alone.

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