Minecraft wiki entry for Allay, associated text: An allay has only one slot on its inventory, allowing it to carry 64 stackable items at once or 16 in case of being ender pearls or snowballs. An allay can carry a single non-stackable item, excluding the one that it holds. If a nearby note block is being played, the allay will instead return items to that particular note block for up to 30 seconds with a vibration particle reaching the allay. It will search for items around the note block.