GET: /server/api/dataElements.json?fields=aggregationType,domainType,categoryCombo,valueType,zeroIsSignificant,name,shortName&filter=domainType:eq:TRACKER&pageSize=1

POST: http://server/api/dataElements

{
    "name": "BCG given (0-11m)",
    "shortName": "bcg",
    "aggregationType": "SUM",
    "domainType": "AGGREGATE",
    "valueType": "NUMBER",
    "zeroIsSignificant": false,
    "categoryCombo": {
        "id": "bjDvmb4bfuf"
    }
}
or 

{
    "name": "BCG given (0-11m) -Test",
    "shortName": "bcg-Test",
    "aggregationType": "SUM",
    "domainType": "AGGREGATE",
    "valueType": "NUMBER",
    "zeroIsSignificant": false
}

Response: 
{
    "httpStatus": "Created",
    "httpStatusCode": 201,
    "status": "OK",
    "response": {
        "responseType": "ObjectReport",
        "errorReports": [],
        "uid": "v3vNs7OnJyR",
        "klass": "org.hisp.dhis.dataelement.DataElement"
    }
}