The Index Stages API provides endpoints to list index stage configuration properties. For more information, view the API specification. An index pipeline is comprised of index stages. Each index stage has a name and a type. The name identifies the stage instance, and the type identifies its class. Every stage type has a number of properties, which can be configured for a particular index stage instance. See the section Index Pipeline Stages for a taxonomy of index stage types. View the configuration properties for index stage type “regex-extractor”: REQUEST 
curl -u USERNAME:PASSWORD https://FUSION_HOST:FUSION_PORT/api/index-stages/schema/regex-extractor
Response 
{
  "type" : "object",
  "title" : "Regex Field Extraction",
  "description" : "This stage allows you to extract entities using regular expressions",
  "properties" : {
    "rules" : {
      "type" : "array",
      "title" : "Regex Rules",
      "items" : {
        "type" : "object",
        "required" : [ "pattern" ],
        "properties" : {
          "source" : {
            "type" : "array",
            "title" : "Source Fields",
            "items" : {
              "type" : "string"
            }
          },
          "target" : {
            "type" : "string",
            "title" : "Target Field"
          },
          "pattern" : {
            "type" : "string",
            "title" : "Regex Pattern",
            "format" : "regex"
          },
          "annotateAs" : {
            "type" : "string",
            "title" : "Annotation Name"
          }
        }
      }
    }
  }
}