Resolution:
Starting the Enterprise Message Service Agent throws the following exception
= = = = = 
Failed to find the start class, "com/tibco/tea/agent/ems/Agent" - bad classpath?
Exception in thread "main" java.lang.NoClassDefFoundError: com/tibco/tibjms/admin/TibjmsAdminException
Caused by: java.lang.ClassNotFoundException: com.tibco.tibjms.admin.TibjmsAdminException
        at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
Unable to find the start class
= = = = =
This exception is thrown when the Enterprise Message Service is not installed on the TIBCO Enterprise Administrator (TEA) server or if the EMS_HOME is not set correctly in the ems-agent.tra file as the Enterprise Message Service agent. It can not find the Enterprise Message Service client JARs needed.

1). Install the Enterprise Message Service on the TIBCO Enterprise Administrator server. 
2). tibco.env.EMS_HOME property in the ems-agent.tra file located in <TEA_HOME>\tea\agents\ems\<ems_agent_version>\bin folder should be updated with the Enterprise Message Service install path. Make sure to include the version number in the path. Example: tibco.env.EMS_HOME=C:/tibco/ems/8.0

Enterprise Message Service-Agent (EMS agent) start up error- Failed to find the start class, "com/tibco/tea/agent/ems/Agent" - bad classpath.

https://docs.tibco.com/pub/tea/2.2.0/doc/pdf/TIB_tea_2.2_ems_agent_guide.pdf