Difference between Costs and Effects
Typically, costs are determined at activation, while effects are determined during resolution of the card.
Notice here, that the controller is required to discard 2 cards in order to meet the activation condition for the card in question. Then, during resolution, the Spell Card is added to the hand.
Now here, there is technically no cost for activating the card, since drawing cards is not considered a cost. This also means that the two-card discard is treated as an effect.