Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given 0 required parameters, 4 optional parameters of different types, no output schema, and no annotations, a one-sentence description is insufficient. The agent cannot determine expected output or which parameters are relevant, especially since url, json, and zone seem unrelated to splitting a hostname.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.