I've heard people say that carrot tops are mildly toxic (I've found this usually means they taste bad or they can cause diarrhea if you eat too much), but other people say they're fine to eat, just not very tasty.
My one experience with carrot tops was quite unpleasant (tasting, no diarrhea).
This website may explain why (it gives recipes too).
The website said that carrot tops can be bitter because they're so high in potassium.
I know from experience and reading that some people are more sensitive to potassium than others. For example potassium chloride is a salt substitute that many people don't find bitter, it tastes pretty much like regular salt to them. Some people though are very sensitive to it, and find the taste extremely bitter and unpleasant (I'm in that category). I once used a small can (only about a cup) of low sodium tomato juice in a huge pot of soup. I didn't notice the potassium chloride in the ingredient list, and it ruined the soup. Even in a huge pot of maybe two gallons of soup, that little bit of potassium chloride was still extremely noticeable to me.
I can see why some people would think it "toxic," because it tastes not only bitter, but metallic. Apparently some people don't taste the potassium, or don't perceive it as unpleasant.