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

There are no annotations, so the description carries the transparency burden. It only says the tool won't return WHOIS/ownership data and gives no information about outputs, side effects, or read-only behavior. The schema's 'discarded' notes add a little transparency, but they are inconsistent with the stated purpose.

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, economical sentence with no unnecessary filler. It is concise and easy to parse, though it could arguably include a brief example or usage note without becoming bloated.

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 is too minimal for the tool's complexity. It doesn't explain what the output looks like, how the many optional parameters interact, or why most parameters are discarded. An agent would not have enough context to confidently call this tool correctly in a real scenario.

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, many are unrelated to splitting a hostname. Params like ref, city, feed, json, and query are described as 'discarded' or 'checked,' but it's unclear why they exist or how they affect the tool. The host param is relevant, but the overall parameter set is confusing and not aligned with the description.

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 clearly states the core action: split a hostname into labels. It also distinguishes itself with the negative qualifier 'without WHOIS or ownership data,' which helps set expectations even if it doesn't name alternative tools.

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 provides no guidance on when to use this tool versus any sibling tools. It doesn't mention alternatives, prerequisites, or typical scenarios, leaving the agent to guess based on the tool name alone.

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