You need to check if tools.jar is set in classpath of Tomcat.
Not aware of Tomcat, but if you are using JBoss server then, open JBoss server from Workspace (from Server view)
Open Launch Configuration -> Select tab "Classpath" -> Expand User Entries -> Add External Jars -> Select path where tools.jar is located (preferably from <JDK installed directory>-> lib) -> Apply -> Restart server once.
This might give hint as to how to configure for Tomcat