During the reign of Emperor Xuanzong of the Tang Dynasty, there was a wealthy man in Chang'an named Yang Chongyi. He owned a parrot with a red beak and green feathers, which was exceptionally intelligent and skilled at mimicking human speech.

One day, Yang Chongyi was murdered by his wife, Liu, who conspired with Li Yan.

The magistrate of Wannian County, relying on the crucial information provided by the parrot, successfully solved the case. Emperor Xuanzong was greatly impressed and bestowed upon this parrot the title 'Green-clad Messenger.'

The scholar Zhang Yue then penned 'A Biography of the Green-clad Messenger' to commemorate its intelligence and unique role.