In my opinion(you can see my whole article in my blog about meta keywords) is to use the correct and appropriate words and phrases as keywords for your meta content.
I think it's absolutely not necessary to add more that you need just because you may hope to get more traffic that way.
I'd also say that if you think 4 words are enough to describe your website, then don't search for more, add those 4 words! You won't gain anything by putting misleading keywords
That's my personal opinion though
