Monkeyman Rewrite Analyzer understand your rewrite rules (“Permalinks”). It is indispensable if you are adding or modifying rules and want to understand how they work (or why they don’t work).
It only analyses , it doesn’t change any rules. It parses rules down to their components and shows the connection with the resulting query variables. Allows you to try out different URLs to see which rules will match and what the value of the different query variables will be. Install and activate, then visit Dashboard -> Tools -> Rewrite analyzer.