...
http://localhost:8080/pentaho/content/ws-run/metadataService/<method-name>
where <method-name> represents the name of a java method of the org.pentaho.common.ui.metadata.service.MetadataService class.
...
doJsonQueryToJson
doJsonQueryToCdaJson
GWT Webservice API
This document does not describe the GWT style of the API. (Community, feel free to add this documentation).