Minecraft wiki entry for ED, associated text: Entity data
Tags common to all entities[show]
Tags common to all mobs[show]
 Size: The size of the magma cube. Note that this value is zero-based, so 0 is the smallest magma cube, 1 is the next larger, etc. The sizes that spawn naturally are 0, 1, and 3.
 wasOnGround: 1 or 0 (true/false) - true if the magma cube is touching the ground.