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

With no annotations, the description carries the full burden of behavioral disclosure. It states the core action but fails to mention that the tool likely discards several parameters (as indicated in the schema descriptions) or clarify how it handles the nine different inputs. The lack of any side-effect or limitation note beyond 'without WHOIS' leaves significant ambiguity.

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 that states the core purpose immediately. It contains no filler and is appropriately concise for the information it conveys.

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 the high schema coverage, the description is incomplete for a tool with nine parameters, many of which are unrelated to the stated purpose (e.g., city, feed, json). It does not explain why these parameters exist or how they relate to the tool's behavior, leaving an agent uncertain about which input to use or what the tool does with the others. The presence of these parameters suggests a broader function not captured in the description.

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 each parameter has a description. The tool description adds no parameter-level detail, but the schema already documents 'host' as the public hostname and marks others as discarded. Since coverage is high, a baseline of 3 is appropriate; the description does not compensate for any gaps but also doesn't need to.

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 the resource ('hostname'), and explicitly notes the absence of WHOIS/ownership data, which distinguishes it from sibling tools like github-repo-shape or figma-url-shape. The verb-resource pair is specific and unambiguous.

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 a use case (when you need hostname labels without ownership info) but provides no explicit guidance on when to choose this over alternatives, nor does it mention any exclusions or prerequisites. It does not reference sibling tools or conditions that would direct an agent.

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