demo-schema.json

{
  "$schema" : "http://json-schema.org/draft-04/schema#",
  "id": "https://gist.githubusercontent.com/Sequoia/d86032bff4413759c2f27e9cf852817b/raw/demo-schema.json",
  "title": "More than one type",
  "description": "This schema has a single property with multiple types",
  "definitions" : {
    "specialString" : {
      "type" : "string",
      "description": "(3) The String One!",
      "enum" : ["yes", "no", "maybe"]
    }
  },
  "properties" :{
    "test" : {
      "description": "a property that can be null, a string, or an object",
      "anyOf" : [
        {
          "type" : "null",
          "description": "(1) The Null One!"
        },
        {
          "type" : "object",
          "description": "(2) The Object One!",
          "properties": {
            "name" : {
              "type": "string"
            }
          },
          "additionalProperties": false
        },
        { "$ref" : "#/definitions/specialString" }
      ]
    }
  }
}

test.json

{
  "$schema" : "https://gist.githubusercontent.com/Sequoia/d86032bff4413759c2f27e9cf852817b/raw/demo-schema.json",
  "test": {
    "badProperty" : "foo",
    "should say 'bad property!' not prompt me to make type null"
  }
}