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

With no annotations, the description carries the full burden of explaining behavior, but it only mentions the core split operation and the absence of WHOIS/ownership data. It does not disclose return format, error cases, or whether the input is a full URL or bare hostname.

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, direct sentence with no wasted words. It conveys the core action immediately and is appropriately concise for a simple utility.

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 not complete enough for correct invocation because the input schema contains irrelevant and misleading parameter descriptions. The tool's actual required inputs and output format are not adequately explained.

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 parameter descriptions are clearly mismatched for this tool: 'url' is described as an HTTPS URL to normalize, 'json' as JSON to validate, and 'zone' as an IANA timezone name. Only 'host' loosely aligns with 'split a hostname into labels,' leaving the agent unable to determine correct parameter usage.

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 tool's primary function: splitting a hostname into labels. This is specific enough to distinguish it from generic URL or JSON tools, though it could be slightly clearer about whether it accepts full domains or subdomains.

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 explicit guidance is provided about when to use this tool versus alternatives like normalize-url or status-catalog. The phrase 'without WHOIS or ownership data' hints at a boundary, but it does not help an agent decide when to invoke this tool in practice.

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