In Kingdom Hearts II, Auto Summon is an action ability that automatically sets the Reaction Command to the name of an available summon when one party member is knocked out and Sora's HP is at critical levels, if summons are usable. The chosen summon changes each time Sora is hit by an enemy attack or combo. Choosing the Reaction Command activates the summon. Auto Summon costs 2 AP to equip, and the normal requirements for summoning apply.
Learning Auto Summon
Kingdom Hearts II