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

With no annotations and no description of side effects, permissions, return format, or error behavior, the agent has no idea what the tool actually does beyond splitting a hostname. No information is provided about whether it performs network calls, modifies data, or returns structured results.

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, but it omits critical information about parameters and usage. It lacks any structure to organize the mismatched parameters or explain which ones are relevant. While brevity is positive, the lack of clarity outweighs the conciseness.

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 mismatched parameters and lack of output schema or return type, the tool is highly incomplete. An agent cannot determine what the tool expects or returns, especially since the parameter descriptions conflict with the stated purpose. This is a significant gap in contextual information.

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?

All four parameters have descriptions, but they are clearly mismatched with the tool's purpose. For example, 'url' is described as 'HTTPS URL to normalize or cite' and 'json' as 'JSON text to validate; discarded after the check'. These have nothing to do with splitting a hostname into labels and are misleading. The descriptions add no value and actively harm understanding.

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 states a clear action (split a hostname into labels) and resource (hostname), but the phrase 'without WHOIS or ownership data' adds ambiguity about what exactly is excluded. It does not clearly differentiate from sibling tools like normalize-url or validate-json, whose purposes are more distinct.

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 the sibling tools. The mention of 'without WHOIS or ownership data' hints at a distinction but is not explicit. There is no indication of appropriate input types or scenarios, leaving the agent to infer usage.

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