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

With no annotations, the description carries full responsibility. It hints at 'without WHOIS or data' implying no external data fetching, but it does not mention side effects, permissions, or the meaning of the discarded parameters.

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 concise, but the wording is awkward and the parameter descriptions (part of the overall structure) are verbose and confusing. The structure of the tool definition as a whole is not clean.

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 does not explain the output format, the relationship between parameters and the operation, or why some parameters are discarded. Given 9 parameters and no output schema, the context is severely incomplete.

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 are misleading and inconsistent; e.g., 'ref' says 'Git ref name; discarded after the shape check', suggesting the parameter is not used. None of the 9 parameters are clearly linked to the hostname splitting purpose, and the descriptions do not add meaning beyond the schema type.

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 splits a hostname into labels, which is a specific action and resource. However, the phrase 'without WHOIS or data' is ambiguous and could be interpreted as not fetching external data, but it's not fully clear.

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 provides no guidance on when to use this tool versus its siblings like normalize-url or browser-url-ok. It does not mention any prerequisites or alternatives.

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