Minecraft wiki entry for BE, associated text: Block entity data
Tags common to all block entities[show]
 author: Author of the structure; only set to "?" for most vanilla structures.
 ignoreEntities: 1 or 0 (true/false): Whether entities should be ignored in the structure.
 integrity: How complete the structure is that gets placed.
 metadata: Value of the data structure block field.
 mirror: How the structure is mirrored, one of "NONE", "LEFT_RIGHT" (mirrored over X axis when not rotated), or "FRONT_BACK" (mirrored over Z axis when not rotated).
 mode: The current mode of this structure block, one of "SAVE", "LOAD", "CORNER", or "DATA".
 name: Name of the structure.
 posX: X-position of the structure.
 posY: Y-position of the structure.
 posZ: Z-position of the structure.
 powered: 1 or 0 (true/false): Whether this structure block is being powered by redstone.
 rotation: Rotation of the structure, one of "NONE", "CLOCKWISE_90", "CLOCKWISE_180", or "COUNTERCLOCKWISE_90".
 seed: The seed to use for the structure integrity, 0 means random.
 showboundingbox: 1 or 0 (true/false): Whether to show the structure's bounding box to players in creative mode.
 sizeX: X-size of the structure, its length.
 sizeY: Y-size of the structure, its height.
 sizeZ: Z-size of the structure, its depth.