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

With no annotations provided, the description carries the full behavioral disclosure burden. It does disclose an important limitation ('without WHOIS or ownership data'), which adds useful context. But it does not describe failure behavior, normalization rules, or the fact that many schema parameters are described as discarded after the call.

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 no filler, and the core behavior is stated upfront. Every word contributes meaning: the operation, the input type, and the key limitation.

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?

Given the tool has seven optional parameters, no annotations, no output schema, and no required field information, one sentence is insufficient. The description leaves an agent unsure which parameter to populate and what the return shape or error behavior looks like.

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 descriptions cover all seven parameters, so the baseline is 3 even without parameter detail in the tool description. The description adds no disambiguation between the `host` property and the numerous other properties like `url`, `path`, or `json`, which is a notable gap given the unusual schema. Still, it does not actively mislead, so the baseline applies.

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 names a specific operation with a clear verb and resource: 'Split a hostname into labels.' The qualifier 'without WHOIS or ownership data' also distinguishes it from domain information lookups. It does not explicitly contrast with sibling tools, but the verb+resource alone makes the tool's role fairly unambiguous.

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?

The description implies that the tool should be used when hostname label splitting is needed and explicitly warns that it will not provide WHOIS or ownership data. However, it does not name alternative tools or conditions for when to prefer this over siblings like normalize-url or other shape-checking tools.

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