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

With no annotations, the description carries the full burden, but it only mentions the basic behavior and a negative. It does not disclose whether the operation is read-only, how invalid hostnames are handled, what the output structure looks like, or that several schema parameters appear to be ignored/discarded.

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, focused sentence with no redundant wording. The negative clause adds valuable information without bloating the text.

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 has nine optional parameters and no output schema, but the description does not explain the expected input format, the output shape, or how to handle the extra parameters. This is insufficient context for an agent to confidently call the tool.

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?

Although every parameter has a schema description, many are unrelated to splitting a hostname (e.g., city, feed, zone, query). The tool description does not map the 'hostname' concept to the appropriate parameter or explain why the other parameters exist, leaving agents uncertain about which inputs are actually relevant.

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 operation: splitting a hostname into labels. It also adds a useful negative constraint ('without WHOIS or ownership data'), which helps distinguish it from ownership/WHOIS tools. However, it does not clarify why the input schema contains many unrelated optional parameters.

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?

No guidance is given about when to use this tool versus related siblings like normalize-url or other shape tools. There is no mention of preferred input type, typical use cases, or conditions that would make this tool the right choice.

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