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

No annotations are provided, so the description carries the full responsibility for behavioral disclosure. It does add a useful negative constraint ('without WHOIS or ownership data'), but it does not state whether the tool is read-only, whether other parameters are processed or ignored, what the output format is, or whether any data is persisted. The schema's repeated 'discarded' notes hint at non-persistence, but the main description omits this entirely.

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 words; every word earns its place. It is slightly too terse given the nine-parameter schema and the absence of output schema, so it is not a perfect 5, but structurally it is efficient and scannable.

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 nine parameters, no output schema, and no annotations, the description is not nearly complete enough. An agent cannot determine what the tool returns for a hostname, whether it also validates URLs/JSON/paths/timezones/search text, or how the 'discarded' behavior works operationally. The description covers only a fraction of the tool's apparent surface.

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 even without parameter details in the description. The description does add some meaning to the `host` parameter by explaining the split into labels, which the schema alone does not. However, it contributes nothing to the semantics of the other eight parameters, so it does not rise above baseline.

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 action ('Split a hostname into labels') and adds a useful boundary ('without WHOIS or ownership data'), so it is not a tautology. However, the input schema exposes nine unrelated parameters (url, json, city, feed, path, zone, query, ref), which the description entirely ignores. This makes the stated purpose narrower than the actual input surface and creates ambiguity about what the tool really does.

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 about when to use this tool versus the many sibling shape tools such as github-repo-shape, figma-url-shape, or jira-key-shape. The phrase 'without WHOIS or ownership data' hints at what is excluded, but it does not explain when domain-shape should be selected or what alternatives exist.

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