For the swagger JSON fields that are not well-defined and schema-less, we can add "additionalProperties" field as follow:

"def1": {
  "properties": {
   "field1": {
      "type": "string"
   }
  },
  "additionalProperties": {
    "type": "object"
 }
}

In C# this should be translated to a property, tagged with [JsonExtensionData] attribute similar to this.

    [JsonExtensionData]
    public Dictionary<string, object> AdditionalProperties { get; set; }

So if there is a schema-less JSON string in the service response, similar to field2 in the following example (for def1 in the swagger spec above), field2 should be serialized to ‘Dictionary<string, object> AdditionalProperties’ property:

{
    "def1": {
        "field1": "this is field 1",
        "field2": {
            "field3": "this is field 3"
         }
     }
}