While ES has its own API endpoints (see https://docs.splunk.com/Documentation/ES/7.0.0/API/AbouttheSplunkEnterpriseSecurityAPI), it mostly uses core Splunk APIs. For correlation searches, use the savedsearches endpoints.
While ES has its own API endpoints (see https://docs.splunk.com/Documentation/ES/7.0.0/API/AbouttheSplunkEnterpriseSecurityAPI), it mostly uses core Splunk APIs. For correlation searches, use the savedsearches endpoints.
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The saved/searches API documentation is at https://docs.splunk.com/Documentation/Splunk/8.2.4/RESTREF/RESTsearch#saved.2Fsearches .
As for which parameters are needed for a correlation search, I recommend using GET on an known correlation search to see which parameters are populated.