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

With no annotations, the description carries the full burden, but it only discloses that WHOIS/ownership data is not used. It does not mention network access, error behavior, output shape, side effects, or how irrelevant parameters are treated.

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, tightly worded sentence with no filler. It front-loads the action and result.

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 nine optional parameters and no output schema, so an agent cannot tell which parameter to populate or what the result will look like. The description is too sparse to fully contextualize the call.

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 a baseline of 3 applies. The overall description adds little beyond the schema; it implies 'host' is the relevant parameter but does not clarify the role of the other eight optional properties.

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 specific action ('Split a hostname into labels') and explicitly excludes WHOIS/ownership data, making the tool's core purpose immediately clear. It also distinguishes this from domain-investigation tools.

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?

No guidance is given about when to choose this tool over the many sibling tools (e.g., normalize-url, fetch-status, github-repo-shape). The 'without WHOIS or ownership data' phrase hints at a boundary, but there is no explicit use-case, alternative, or condition.

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