For @p, @r and @a are discriptions, but for @e is no discription (yet) in commandblocks. They might forget to add that, but it is still a bug, because there has to be a discription for that.
MC-44651
For @e is no description inside commandblocks
Resolved
Fixed
3
(Unassigned)
Confirmed
command, command_block, entity
Minecraft 14w02b, Minecraft 14w02c, Minecraft 14w03b, Minecraft 14w04b, Minecraft 14w05b, Minecraft 14w06a, Minecraft 14w06b
Minecraft 14w08a
Retrieved
Confirmed for 14w06a/b