画蛇添足是一个寓言故事演化而成的成语，最早出自《战国策·齐策二》，比喻做了多余的事，非但无益，反而不合适。

This is an idiom evolved from a fable, originally from "Warring States Policy: Qi Ce II". It is a metaphor for doing superfluous things, which is not only useless, but inappropriate.