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

No annotations are present, so the description carries the full burden of behavioral disclosure. It only states the split and the absence of WHOIS/ownership data, but does not disclose expected input, output format, network behavior, or how the json and zone parameters are handled.

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. The qualifier 'without WHOIS or ownership data' usefully sets expectations, though the description could be slightly more informative without losing conciseness.

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?

With no output schema, no annotations, and four optional parameters, one sentence leaves too much unspecified: which parameter represents the hostname, what the output looks like, and what happens when url, json, or zone are provided. The schema clarifies individual parameters but not the overall invocation contract.

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 a baseline of 3 applies. The schema already explains url, host, json, and zone semantics; the description adds little about which parameter to use for splitting a hostname, but it does not need to compensate for missing schema information.

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', and adds a boundary by excluding WHOIS/ownership data. It is not a tautology and conveys the core function, but it does not differentiate among the four input properties or name sibling tools, so it stops short of a top score.

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?

There is no guidance on when to use this tool versus alternatives, and no sibling tools are mentioned. The phrase 'without WHOIS or ownership data' only hints at scope; it does not explain when to pass url vs host or when not to use the tool.

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