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

With no annotations provided, the description carries the behavioral disclosure burden. It usefully discloses that no WHOIS or ownership data is involved, suggesting a pure syntactic operation. However, it does not explain how extra schema fields are treated, whether the operation is read-only, or what happens with invalid hostnames.

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 sentence with no filler. The verb and object are front-loaded, and the exclusion of WHOIS/ownership data earns its place by setting important scope boundaries.

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?

Despite a very clear one-line purpose, the definition is incomplete for actual invocation. There are 9 optional parameters, no annotations, and no output schema, yet the description does not say which field to use, what the split result looks like, or whether multiple fields are allowed. An agent could plausibly pass the wrong parameter.

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 reinforces that a hostname is the target, which maps to the 'host' parameter, but it does not clarify that among the 9 optional parameters the agent should use 'host' or that the other fields are ignored. This weakens its added value for parameter selection.

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. It also adds a clear boundary by saying 'without WHOIS or ownership data', which distinguishes this from enrichment-style domain tools and makes the tool's role obvious.

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 implies this tool is for hostname labeling and not for ownership/WHOIS queries, but it never names an alternative tool or explicitly explains when to choose domain-shape over siblings like github-repo-shape, figma-url-shape, or jira-key-shape. The usage context is only implicit.

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