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

With no annotations, the description carries the full behavioral burden, and it does disclose that the tool does not provide WHOIS or ownership data. However, it does not state whether other inputs are ignored, whether network/DNS access occurs, or anything about side effects or output behavior.

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, front-loaded sentence with no filler. It communicates the core action immediately and adds a meaningful qualifier without repeating the tool name or schema details.

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 nine optional parameters, no annotations, and no output schema, this one-sentence description is insufficient. It does not specify which parameter to pass, what happens if no parameter is supplied, or what the return value looks like, and it leaves the unrelated schema fields unexplained.

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?

Schema description coverage is 100%, so the baseline is 3. The description adds minimal parameter meaning beyond the schema: it aligns with the 'host' field, but it does not clarify that host is the only relevant parameter among the nine optional fields or explain how the other fields relate.

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 specific operation: split a hostname into labels, and adds the useful scope qualifier 'without WHOIS or ownership data.' This clearly distinguishes it from URL, file, and repo shape tools among the siblings, though it does not name an alternative.

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?

There is no explicit guidance on when to use this tool versus alternatives like normalize-url or other shape tools. The word 'hostname' implies the use case, but the description never states when not to use it or which sibling tools apply to URLs, files, or other inputs.

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