OpenSearch/rest-api-spec/api/cluster.settings.json

{
  "cluster.settings": {
    "documentation": "http://elasticsearch.org/guide/reference/api/admin-cluster-update-settings/",
    "methods": ["GET", "PUT"],
    "url": {
      "path": "/_cluster/settings",
      "paths": ["/_cluster/settings"],
      "parts": {
      },
      "params": {
      }
    },
    "body": {
      "description" : "The settings to be updated. Can be either `transient` or `persistent`."
    }
  }
}