Is it right to have merely one keyword phrase in Meta Tag?

[isismedia]

The site that I created lately has over 50 pages that are effectively optimized for specific keywords and keyword phrases. According to me, the density is also perfect and even the interlinking is quite appreciable. Now, I was working on the Meta tags. But, I couldn’t figure out whether I should use one keyword phrase or all the keywords.


What I had thought was to include a target phrase in the keyword tag. Can you please inform me if there is any downside? What do you suggest; one target keyword phrase or all the keywords will work fine in the Meta keyword space?