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

With no annotations, the description carries the behavioral disclosure burden. It does reveal that the tool performs a pure shape-style split and will not return WHOIS or ownership data, which is useful. However, it does not disclose whether other schema fields are ignored, whether network access is involved, or what the returned labels look like.

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 short, front-loaded sentence with no filler or repetition. It efficiently communicates the main operation and a key limitation, though the brevity leaves contextual gaps elsewhere.

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 nine optional parameters, no annotations, and no output schema, this terse description is not complete enough for confident invocation. The agent must guess that host is the relevant parameter and is left without information about the response structure or how the other accepted parameters are handled.

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 each parameter is already individually documented. The description adds the idea of splitting a hostname into labels, but it does not clarify whether host is the only meaningful parameter or how to format it beyond the schema's 'public hostname' description.

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 concrete operation: split a hostname into labels. It also clarifies a relevant non-goal by saying WHOIS or ownership data are not included. It does not explicitly position itself against siblings like normalize-url or github-repo-shape, so it stops short of full differentiation.

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 guidance on when to use domain-shape instead of related tools, nor does it say when not to use it. The phrase 'without WHOIS or ownership data' implies a shape-only use case, but no alternatives or selection conditions are mentioned.

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