Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's low complexity (basic arithmetic), two parameters, no annotations, and the presence of an output schema (which handles return value documentation), the description is complete. It covers the operation, parameters, return value, and error conditions, leaving no significant gaps for this straightforward tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.