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

No annotations are provided, so the description carries the full burden. It only mentions the split operation and the absence of WHOIS/ownership data; it does not disclose output format, error handling, side effects, or whether any network access occurs.

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 sentence with the action front-loaded and no wasted words. It is concise, though the brevity leaves out operational details.

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 no output schema, no annotations, four optional parameters, and ten sibling tools, the description is incomplete. It does not describe the return value, which parameter to pass, or how invalid inputs are handled, and the unrelated parameters are left unexplained.

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. The description adds no parameter-level guidance and does not clarify whether 'host' or 'url' is the intended input, nor why 'json' and 'zone' appear for a hostname-splitting tool.

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 verb and resource: 'Split a hostname into labels.' It also adds a scope exclusion ('without WHOIS or ownership data'), which helps clarify what the tool does not do. However, it does not explicitly distinguish this from siblings like normalize-url.

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 alternatives. The phrase 'without WHOIS or ownership data' implies it is not for ownership lookups, but it names no alternative tools or conditions for selection.

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