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

With no annotations provided, the description carries the full burden of behavioral disclosure. It only states an exclusion — no WHOIS/ownership data — and does not disclose what happens to inputs like url, json, or zone, whether the operation has side effects, or what the split output looks like. The schema hints that json is discarded, but the description adds no behavioral context.

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 sentence with zero filler. The main verb and resource are front-loaded, and the exclusion clause is efficient. Every word contributes meaning.

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 tool exposes four diverse optional parameters but the description explains only the hostname-splitting behavior, leaving url, json, and zone unexplained in terms of how they relate to the tool's purpose. With no output schema and no annotations, an agent lacks key information about return values and how the parameters interact.

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 schema already documents all four parameters, warranting the baseline 3. The description adds implicit meaning for 'host' via 'hostname' but does nothing to clarify why url, json, and zone are accepted by a tool described solely as a hostname splitter.

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 uses a specific verb ('split') and resource ('hostname into labels'), making the core action clear. The 'without WHOIS or ownership data' clause draws a scope boundary that helps distinguish it from enrichment or lookup tools, though it does not explicitly name a sibling tool.

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?

No guidance is given on when to use this tool versus any alternative. There is no mention of when the tool is appropriate, what inputs it expects in practice, or what to use instead when WHOIS/ownership data is needed.

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