I agree with Ryan. The one thing to consider is whether redirects will help or hurt your site. Even websites that are appropriately redirected lose some link equity in the process. See Matt Cutts' video here which says that roughly 10-15% of PageRank is lost through redirects and outgoing links. Therefore, if the site has existed using the format domain.com/post-name for a long time and attracted links to those URLs, then the small benefit you get from redirecting to domain.com/keyword/post-name may be outweighed by the natural loss of link equity.
Liberating Your Data from Google Webmaster Tools - a Step-by-Step Guide
5/11/2012 How to use XAMPP to collect crawl error data (and more) from Google Webmaster Tools via their API.