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

With no annotations, the description carries the full burden of disclosing behavior. It only states the primary function and vaguely notes the absence of WHOIS/data. It does not indicate whether the operation is read-only, whether it performs network calls, or how it handles invalid inputs.

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, which is concise. However, the trailing phrase 'without WHOIS or data' is confusing and could be removed or reworded; it does not earn its place because it introduces ambiguity rather than clarity.

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?

There is no output schema, so the description should explain the return format. It does not state whether the output is an array of labels, how errors are reported, or how to handle the many irrelevant parameters. This lack of context makes the tool difficult to use correctly.

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?

The schema provides descriptions for all parameters, so the baseline is 3. The tool description adds no extra value about parameter usage; it does not clarify which of the nine parameters is relevant (e.g., 'host') or explain why many unrelated parameters exist in the schema.

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 core action is clear: splitting a hostname into labels. The verb 'split' and resource 'hostname' are specific. However, the appended phrase 'without WHOIS or data' is ambiguous and mildly obscures the primary purpose.

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 usage when a hostname needs to be split, but it does not explicitly state when to prefer this tool over siblings or mention alternatives. The phrase 'without WHOIS or data' hints at a limitation but offers no concrete guidance on tool selection.

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