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

With no annotations, the description carries the full burden. It openly describes the transformation and the absence of WHOIS/ownership data, which suggests a read-only utility. However, it does not explain how the tool handles the multiple accepted input parameters or what happens on invalid input.

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?

A single sentence with no filler. The key action is front-loaded, and the qualifying phrase adds useful scoping without bloating the description.

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 description covers the core purpose and suggests the output (labels), but with no annotations and no output schema, it leaves the relationship among the four optional parameters unclear. An agent can likely infer how to call it, but the missing parameter-selection guidance is a noticeable gap.

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 extra parameter-level meaning, and the schema already documents each parameter. It also does not clarify why parameters like json and zone are relevant to hostname splitting.

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 uses a specific verb ('split') and resource ('hostname into labels'), and adds an explicit exclusion ('without WHOIS or ownership data') that sharpens the boundary. This clearly differentiates it from sibling tools like normalize-url, validate-json, and timezone.

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 explicit guidance about when to use this tool versus the sibling alternatives, nor any mention of what to use if WHOIS or ownership data is needed. The description implies a use case but does not state it as guidance.

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