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

With no annotations, the description carries the behavioral disclosure burden, and it explicitly states the key limitation: no WHOIS or ownership data is fetched or included. The described behavior is a non-destructive local split operation, so the absence of side-effect details is not a serious gap.

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 one tightly worded sentence with the core operation front-loaded and the limitation appended concisely. There is no filler, repetition, or unnecessary elaboration.

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 description gives a clear purpose, but with no output schema and many optional parameters it does not state required inputs, the return format, or how to route between domain-shape and sibling shape/url tools. The schema's parameter descriptions partly compensate, but tool-level invocation details are left to inference.

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 parameter-level detail. The only indirect link is 'hostname' in the description matching the schema's 'host' parameter, but no new semantics beyond the schema are provided.

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 operation ('split a hostname into labels') and a clear resource, with the qualifier 'without WHOIS or ownership data' scoping it as a lexical parse rather than a lookup. This helps distinguish it from sibling URL/status/shape tools such as normalize-url, fetch-status, and figma-url-shape.

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?

Usage context is only implied: the tool should be used when hostname labels are needed and WHOIS/ownership data is not. It does not explicitly state when to use this tool versus alternatives, nor does it name any sibling tool as a fallback, despite many closely related siblings.

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