Decision-making occurs when you have multiple options. When you are evaluating the worthiness of a decision, you use calculation and prediction. Calculation requires you to add up the facts: known numbers and odds. Prediction requires you to mentally juggle possible reactions to your decisions, reactions that are not calculable or predictable; well, perhaps predictable if your opponent always plays rationally and to his or her maximum benefit, or has a blind-spot, but not predictable as in mathematically "set in stone".
Some amount of calculation is ok. Too much calculation is boring. Poker against the house is pure calculation, and ultimately futile; you only have one "right" decision, which you can arrive at after much calculation, and it's never going to win in the long run. Poker against other players also requires calculation, but also a lot of incalculable prediction, and is therefore more interesting, at least as far as decision-making goes. Caylus, and several other meaty Eurogames I could name, favor too much calculation in the decision-making process.
Your game is fiddly if you mistake calculation for decision-making.