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 mentions that the tool avoids WHOIS/ownership data, which is useful, but it does not explain how it handles the many other input parameters (ref, url, json, path, etc.) or what the output looks like. The behavior for non-hostname inputs is completely unknown.

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 and is technically concise. However, it is under-specified to the point of being unhelpful, so it does not earn credit for effective 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 tool's complexity (9 parameters, no required fields, no output schema), the description is gravely incomplete. It does not explain what 'labels' means, how the output is structured, or how to select the correct input among many. An agent would struggle to invoke this tool correctly based solely on 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?

Although the schema descriptions cover all parameters (100%), the tool description does not clarify which parameters are actually relevant to the stated purpose. It adds no insight beyond the schema, and given the large number of seemingly unrelated parameters (city, feed, zone), an agent could be misled into thinking all are valid inputs for the hostname splitting operation.

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 the resource (hostname), but it does not specify which of the 9 input parameters should be used to provide the hostname. This ambiguity makes it difficult for an agent to know how to call the tool correctly. It also does not differentiate from sibling tools like normalize-url or browser-url-ok.

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 guidance on when to use this tool versus alternatives. The description does not mention any trade-offs or prerequisites, leaving the agent to infer that it is appropriate for any hostname-related task, which may be incorrect.

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