WSO2 products currently do not have a documented service API. However you can use OSGi console to view the available service components details.
Make sure that when you start WSO2 IS with osgi console the following log is visible, which says that the console is enabled.
sh wso2server.sh -DosgiConsole
JAVA_HOME environment variable is set to /jdk1.6.0_30
CARBON_HOME environment variable is set to /wso2is-4.1.0
OSGi console has been enabled with options: -console
After server is properly started, press enter and osgi> console will be displayed.
[2013-07-24 16:33:57,215] INFO {org.wso2.carbon.core.internal.StartupFinalizerServiceComponent} - WSO2 Carbon started in 17 sec
[2013-07-24 16:33:57,437] INFO {org.wso2.carbon.ui.internal.CarbonUIServiceComponent} - Mgt Console URL : https://localhost:9443/carbon/
osgi>
By entering necessary osgi commands you can see the activated OSGI service etc. For example if you need to see available services use,
osgi> services
This will list down all the services in the runtime. Use appropriate filters to find the WSO2 IS services by referring this blog post.
osgi> ls
This shows all the osgi service components along with their component ID and life-cycle status. If you need to now on particular service component use ls -c command.
The following question thread has useful information on WSO2 IS API too.
WSO2 identity server api