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

With no annotations, the description must disclose side effects and behavior. It implies a pure transformation ('Split') and clarifies what it does not return, but it does not mention read-only status, error behavior, or whether input is stored, so transparency is incomplete.

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 an active verb and a useful negative clarification. It is concise and front-loaded.

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 four parameters and no output schema, the description is too sparse. It does not say which parameter is required, how the parameters interact, or what the resulting labels look like, leaving important context missing.

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, the tool description does not connect 'hostname' to any specific parameter, and url, json, and zone appear unrelated to splitting hostnames. The descriptions read as if copied from other tools, so the parameter semantics are confusing rather than clarified.

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 concrete action ('Split a hostname into labels') and a useful negative scope ('without WHOIS or ownership data'), but it does not clarify which of the four unrelated parameters (url, host, json, zone) should be used, leaving the core purpose somewhat ambiguous.

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 on when to use this tool versus sibling tools such as normalize-url or iana-zones. The only comparative hint is the negative phrase about WHOIS/ownership, which is not enough to guide selection.

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