A literal translation of "savoir faire" might be "to know what to do."
But does it apply to knowledge, skill, "polish," or something similar?
And is the English word "savvy," which appears to be a "cognate," a good translation for it?
Savoir-faire is a canonical phrase meaning that one knows how to do something. It does apply to knowledge, but more for hands-on knowledge or skill than general knowledge, as faire does mean "to do". So as you pointed it our, it's like "to know what/how to do".
Savoir-faire is used as noun only and can be understood as a set of skills or general knowledge of what to do in a situation.
Although is can be used as is in English, I think the more appropriate translation and concept in English is know-how, but savvy is also in the right direction.