The long belongs to water. This is the single fact from which most of the rest follows, and it is the one most often lost in translation.
Long govern rivers, lakes, seas, wells and above all rain. The dragon kings of later tradition rule the four seas and are addressed in drought: temples were built to them, offerings made, and imperial officials could be held responsible for arranging the petition. A creature one asks for rain occupies a completely different position in a society from a creature one sends knights to kill.
Its form is serpentine and long-bodied, with four short clawed limbs, horns or antlers, whiskers, and a scaled body. It has no wings. Its movement through cloud and water is its own, and Chinese depictions place it among swirling vapour rather than in flight. A classical description enumerates it as a composite of parts belonging to nine other animals, the horns of a stag, the head of a camel, the eyes of a demon, the neck of a snake, the scales of a carp, the claws of an eagle, the paws of a tiger, the ears of an ox, which is a way of saying that it is the sum of animal power rather than a distinct species.
It is auspicious. Its appearance is a good omen, not a crisis. There is no Chinese equivalent of the dragon-slaying narrative, and the absence is total rather than incidental: the story type does not exist because the creature does not occupy the role that would require it.