It is a very common grammatical error to confuse the word good with the word well. Many folks use these two terms interchangeably to mean fundamentally the same thing. That’s a mistake. The name of the coffee shop shown above (It’s All Good) is correct, because it is stating that everything available at this coffee shop is good. It would not be correct, however, to call it the It’s All Well Cafe. That doesn’t make grammatical sense.
Good is an adjective. It is used to describe a noun. This is a very good sandwich. Jim Balsillie is very good at what he does for a living. The word good is used to modify or describe the sandwich and Mr. Balsillie. It would not be correct so say that the sandwich is very well.
Well is an adverb. It functions in much the same way as the word easily in that it describes how something is done. An adverb is used to describe a verb. Tiger Woods plays golf very well. Donald Trump manages his business well. We’re saying how Tiger and Donald are playing and managing. It would not be correct to say that Tiger plays good.
In regards to health, it seems perfectly acceptable to say that you are well. This is because well is still being used as an adverb. It is describing how you are doing. In essence, you are omitting the word doing from your response.
I am well. = I am doing well.
If you were to respond by saying that you are good, the meaning would be quite different. By saying that you are good, you are saying that you are a good person, implying that you are caring, generous, and so on. This does not accurately respond to the question, “How are you?”
Well, what are you waiting for? Get out there and do some good.