[rules-users] Eclipse Drools Project external jar

Hello, I think I have a pretty trivial qeuestion, but still, I cannot come up with an answer. I'm exploring drools and I have a little Drools project in Eclipse, created using the drools plugin ver. 4.0.4. I can include classes defined in the project in the guided editor, but not classes that I added to the build path and imported using the rule.package file. How do I use the external jars in BRLs ? Also, if I add the import to DRL, does the IDE supposed to throw an error if that class is not found in any referenced jar ? Thanks.