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

No annotations are provided, and the description does not mention output format, error behavior, side effects, or whether the operation is purely syntactical beyond the 'without WHOIS' note. The agent is left to infer basic runtime behavior.

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 concise sentence with no redundant wording. It front-loads the main action and adds a brief scope qualifier, though it could include a little more practical detail without becoming verbose.

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 optional parameters, no output schema, and no annotations, the description is too sparse for an agent to confidently call the tool. It does not specify the input parameter, expected result shape, or failure conditions.

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 schema descriptions cover all parameters, but the tool description does not explain how the nine optional parameters relate to the hostname-splitting operation. The presence of unrelated parameters such as city, zone, and json creates ambiguity about which input is actually used.

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 clearly states the core action: split a hostname into labels. The phrase 'without WHOIS or ownership data' also gives a useful negative scope, distinguishing it from ownership lookups. However, it does not explicitly say which parameter should contain the hostname.

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 sibling tools like normalize-url, browser-url-ok, or file-path-ok. The only hint is a negative statement about WHOIS/ownership data, which is not enough to direct an agent's decision.

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