Hi,
You can found a class inside a jar file for instance in this way: https://stackoverflow.com/questions/1500141/find-a-jar-file-given-the-class-name
Can you also try to find if any file with the pattern name xmltooling*.jar exists in the server.
Regardless the outcome of it, I would try to add xmltooling-1.4.1.jar to weblogic PRE_CLASSPATH. On the weblogic startup scripts (setDomainEnv.sh I guess) you can add/modify the PRE_CLASSPATH variable. I would copy xmltooling-1.4.1.jar to some directory and add the full path of the jar to the pre_classpath.
Regards