Spell identifying

A player can use a reaction while a caster is (perceptibly) casting a spell, or an action after the spell has been cast, to try and identify the spell. When the player uses this, the character can roll an Intelligence (Arcana) check. The DC equals 15 + the spell's level. If the spell is cast as a class spell, and the identifying character is a member of that class, the check is made with advantage.