Daily Chinese Idiom Guessing Game
sharp and discerning eyes; ability to see through deception or false appearances.
原指《西游记》中孙悟空能识别妖魔鬼怪的眼睛◇用以形容人的眼光锐利，能够识别真伪。
元·杨景贤《西游记杂剧》第三本第九出这厮瞒神唬鬼，铜筋铁骨，火眼金睛。”
With his 火眼金睛, the detective easily spotted the forgery.