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

No annotations are present, so the description carries the full burden for behavioral disclosure. It does add one useful boundary ('without WHOIS or ownership data'), but it fails to state whether the operation is read-only, what the output looks like, how labels are returned, or that most input parameters like ref, city, and json are discarded rather than used.

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 with no wasted words and the core action is front-loaded. It is concise and scannable.

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?

Despite a simple stated purpose, the tool has 7 parameters, no output schema, and no annotations, so the one-sentence description is insufficient. It doesn't identify which parameter is used, what the return value is, whether other parameters are ignored, or any side effects. An agent would need extra inference before calling this tool 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 already documents all 7 parameters with per-property descriptions, so schema coverage is high and the baseline is 3. The tool description does not explicitly map 'hostname' to the 'host' parameter, but the schema's 'Public hostname' description makes that connection clear enough. The description adds no significant parameter semantics beyond the schema.

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 uses a specific verb and resource: 'Split a hostname into labels'. It also adds the clarifying scope 'without WHOIS or ownership data', which helps distinguish the tool from ownership-oriented lookups. However, it doesn't name or contrast sibling 'shape' tools, so differentiation is implied rather than explicit.

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 implies the tool is for hostname shape analysis but provides no explicit guidance about when to choose this tool over alternatives like github-repo-shape, figma-url-shape, or normalize-url. There are no exclusions, prerequisites, or alternative conditions stated.

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