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

With no annotations, the description carries the full burden of explaining behavior. It only states a negative constraint ('without WHOIS or ownership data') and fails to mention what the tool returns, possible side effects, or error conditions. The schema contains unrelated fields (e.g., 'Git ref name', 'City name') that create confusion about actual behavior, reducing transparency.

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, concise sentence that avoids unnecessary words. It is easy to read and does not include fluff. However, it could be structured to include more relevant details without becoming verbose, so it does not earn full marks for structure.

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?

The description is highly inadequate for correct invocation. With 9 optional parameters, none of which are clearly tied to the hostname mentioned in the description, the agent cannot know what inputs to provide or what output to expect. There is no explanation of the tool's behavior beyond the basic split action, making it impossible to use correctly without external knowledge.

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 parameter descriptions in the schema are inconsistent with the tool's stated purpose. For example, 'ref' is described as a Git ref name, and 'city' as a city name, neither of which relate to splitting hostnames. The tool description does not map the hostname input to any of the listed parameters, leaving the agent unable to determine which parameters are relevant or how they should be populated.

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 tool's purpose: splitting a hostname into labels, using a specific verb and a clear resource. However, it does not explicitly distinguish itself from sibling tools like normalize-url or web-fetch, though that is not strictly required for purpose clarity.

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 lacks any guidance on when to use this tool versus alternatives, such as normalize-url or web-fetch. There are no preconditions, typical scenarios, or hints about the context in which the tool should be invoked, leaving the agent without sufficient direction.

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