Simms spent some years of his life in Saudi Arabia, where his parents were school teachers. He graduated from Harvard University, where he wrote for the Harvard Lampoon and was a part-time student security guard, often during the night shift. He began his career in television writing for Late Night with David Letterman. Simms later wrote for the HBO program, The Larry Sanders Show. He was the creator and head writer for the NBC sitcom, NewsRadio. More recently, he has directed and produced for the HBO series The Flight of the Conchords. He has also contributed pieces to The New Yorker. He also wrote a sitcom pilot, Beach Lane, starring Matthew Broderick, for executive producer Lorne Michaels.