At the moment of use
The contract answers the caller's questions before failure turns into delay.
Most integration pain comes from uncertainty that was never resolved early enough. What does this field really mean? Which values are allowed? Does this action create, assign, or merely request? Runtime clarity makes those answers available before the caller has to guess.
That keeps the interaction closer to inspection and farther from trial and error.
Field meaning
AIXE expects fields to be explained in business terms so a caller can map inputs to outcomes with less ambiguity.
Execution boundaries
The contract shows where the action starts, what it needs, and what the system refuses to assume on the caller's behalf.