So, you (believe) you've configured the agent to protect your application URLs as part of your SSO implementation.
You attempt this by accessing the application URL and you're 302 re-directed to the forgeRock OpenAM login screen (so far so good).
When you initiate the OpenAM instance within a tomcat container, you'll see within the catalina log file the initial error 'SEVERE: Begin event threw error' error followed by 'java.lang.ExceptionInInitializerError error'
When deploying the agent within your local environment or deploying from eclipse, you'll likely come across the
'java.lang.ClassNotFoundException: com.sun.identity.agents.filter.AmAgentFilter' error when compiling or deploying to a particular server.
When integrating with the OpenAM and an application, I would receive a syntax error when trying to populate the application with the filter as part of the web.xml population. You can see the display-name error when working with the eclipse IDE.