As a best practice, input parameters should be high up the logic, with no or as little as possible dependencies / conditional logic on them.
The reason is that the very same logic that is used for outputs computation is also used for parameter determination. You can use api.isSyntaxtCheck() API call which determines which code does not need to be run in the parameter determination mode and should be called only in the real computation (like expensive DB calls).
Example:
def inputVal = api.userEntry()
if (api.isSyntaxCheck()) return;
def costs = api.find("PX", equal("name", "costs"))