In an early version, the agent fabricated eight client names even though the underlying tools were returning real records. It also produced incorrect counts, sums, and averages when asked to reason over large raw result sets.
My first fix was to introduce a deterministic query workflow for filtering and aggregation. Surprisingly, evaluation accuracy dropped from 30% to 20%. The workflow itself was correct; the agent simply continued choosing the older raw-data tools whenever they remained available.
Removing those tools entirely and constraining the agent to parameterized deterministic operations improved final accuracy to 60%.