Minecraft wiki entry for Other_data_format, associated text: : Parent tag.
 EntityIdentifier: The id of the entity to be summoned.[more information needed]
 Delay: Ticks until next spawn. If 0, it spawns immediately when a player enters its range.
 MinSpawnDelay: The minimum random delay for the next spawn delay.
 MaxSpawnDelay: The maximum random delay for the next spawn delay.
 SpawnCount: How many mobs to attempt to spawn each time.
 MaxNearbyEntities: The maximum number of nearby (within a box of SpawnRange*2+1 × SpawnRange*2+1 × 8 centered around the spawner block[needs testing]) entities whose IDs match this spawner's entity ID.
 RequiredPlayerRange: Overrides the block radius of the sphere of activation by players for this spawner.
 SpawnRange: The radius around which the spawner attempts to place mobs randomly. The spawn area is square, includes the block the spawner is in, and is centered around the spawner's x,z coordinates - not the spawner itself.[needs testing] Default value is 4.
 DisplayEntityWidth: The width of entity model that displayed in the block.
 DisplayEntityHeight: The height of entity model that displayed in the block.
 DisplayEntityScale: The scale of entity model that displayed in the block.
 SpawnData: (May not exist) Contains tags to copy to the next spawned entity(s) after spawning.
 Properties: Unknown.
 TypeId: The entity's namespaced ID.
 Weight: Unknown.
 SpawnPotentials: (May not exist) List of possible entities to spawn.
: A potential future spawn.
 Properties: Unknown.
 TypeId: The entity's namespaced ID.
 Weight: The chance that this spawn gets picked in comparison to other spawn weights. Must be positive and at least 1.