Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Given the tool's complexity (special values, admin requirements, error conditions, output details), the description covers all aspects: the key_id special cases, permission model, 409 failure mode, result format, and cost. It even explains the behavior of the 'others' case in detail. An agent armed with this description can invoke the tool correctly in every scenario.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.