눈치깠어 Nunchi Kkasseo

"눈치 Nunchi " refers to the ability to notice other people's feelings or situations very quickly.
So, Korean say, "Take notice of it" to respond appropriately to the situation.
On the other hand, "눈치까다", "눈치깠어", etc. are used to say,
When someone tries to deceive someone, if you notice it in advance, you say, 그가 눈치깠어. 알아챘어. "He noticed it." 

 
When you try to prepare a Surprise party for Tom's birthday, but Tom already knows about the party preparations based on the overall situation,
We say, "Tom noticed it." Tom이 눈치깠어.  Nunchi Kkasseo

source: https://ko.wikipedia.org/wiki/%EB%88%88%EC%B9%98#:~:text=%EB%88%88%EC%B9%98(%EB%AC%B8%ED%99%94%EC%96%B4%3A%20%EB%88%88%EA%B8%B0)%EB%8A%94,%EC%9C%A0%EC%A7%80%EC%8B%9C%ED%82%A4%EA%B8%B0%20%EC%9C%84%ED%95%9C%20%EC%88%98%EB%8B%A8%EC%9D%B4%EB%8B%A4.