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

Without annotations, the description carries the full burden. It mentions the tool does not return WHOIS or data, which is a behavioral note, but it does not disclose side effects, permissions, or the exact nature of the output. The 'discarded after the check' hint for the json parameter is buried and not tied to the main action.

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, efficient sentence that states the core function. It is appropriately concise, but it lacks any structured breakdown of inputs or outputs, which slightly reduces the score.

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 no output schema and no annotations, the description must be self-sufficient. It does not specify which parameter is the hostname, what the output format is, or how the parameters relate to the action. The tool is far from complete for an agent 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 input schema includes four parameters (url, host, json, zone), each with descriptions unrelated to the tool's purpose. The description does not explain which parameter is the hostname or how the others relate to splitting a hostname. The parameter descriptions are contradictory and misleading, and the tool description adds no clarifying meaning.

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 action ('Split a hostname into labels') and what it does not do ('without WHOIS or data'). However, it does not clarify which of the four parameters is the hostname, introducing ambiguity about the input.

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?

No guidance is provided on when to use this tool versus alternatives. The description does not mention any sibling tools, conditions, or scenarios where this tool is preferred.

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