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

No annotations are present, so the description carries the full burden. It discloses that the tool does not provide WHOIS or ownership data, which is useful. However, it does not describe the output format, whether it validates hostname syntax, or how invalid inputs are handled. The behavior is only partially transparent.

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 11-word sentence with no fluff. The verb and object are front-loaded, and every word earns its place. The negative qualifier 'without WHOIS or ownership data' adds important distinction without unnecessary length.

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 tool is simple, but the description is inadequate relative to the complex schema. It does not specify which input parameter should be used, what the return value looks like, or how to handle the many unrelated schema fields. There is no output schema, and the mismatch between the description (hostname-focused) and the schema (many input types) leaves the agent uncertain about correct invocation.

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?

The input schema contains seven properties with individual descriptions, including 'host' described as 'Public hostname', which aligns with the tool's purpose. Schema coverage is high (100%), so the baseline is 3. The description does not map the 'hostname' concept to the 'host' parameter, nor does it clarify why unrelated parameters (e.g., 'city', 'json') appear in the schema. No added value beyond the schema.

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 'Split a hostname into labels without WHOIS or ownership data' clearly states a specific verb ('split') and resource ('hostname'), and explicitly distinguishes itself from WHOIS/ownership lookup tools. The purpose is unambiguous and aligns with the tool name, setting it apart from siblings like 'figma-url-shape' or 'github-repo-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?

The description implies usage: when a hostname needs to be split into labels. However, it does not explicitly mention alternatives, when not to use the tool, or compare to closely related siblings like 'normalize-url' or 'web-fetch'. No exclusions or conditions are provided, so usage guidance is only implicit.

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