398.2. Limited Actions
398.2.a. A Limited Action is a game action that a spell, ability, or circumstance of the turn's progression causes the player to perform. A player cannot perform these actions at-will.
398.2.b. These actions can only be taken when a player is instructed to do so as the execution of an effect or during their specified occasion during the turn. Example: A player may Draw during the Draw Step of the Beginning Phase of their turn or when instructed to do so by a spell or ability. They can't choose to Draw at any other time.