animals with additionalProperties allowed

animals.json

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "oneOf": [
        {
            "description": "a single animal",
            "$ref": "#/definitions/animal"
        },
        {
            "description": "a collection of animals",
            "type": "array",
            "minItems": 1,
            "uniqueItems": true,
            "items": { "$ref": "#/definitions/animal" }
        }
    ],
    "definitions": {
        "common": {
            "type": "object",
            "required": [ "type", "name" ],
            "properties": {
                "name": { "type": "string" }
            }
        },
        "cat": {
            "allOf": [
                { "$ref": "#/definitions/common" },
                {
                    "required": [ "favoriteToy" ],
                    "properties": {
                        "type": { "enum": [ "cat" ] },
                        "favoriteToy": { "type": "string" }
                    }
                }
            ]
        },
        "dog": {
            "allOf": [
                { "$ref": "#/definitions/common" },
                {
                    "required": [ "breed", "leashColor" ],
                    "properties": {
                        "type": { "enum": [ "cat" ] },
                        "breed": { "type": "string" },
                        "leashColor": { "type": "string" }
                    }
                }
            ]
        },
        "animal": {
            "oneOf": [
                { "$ref": "#/definitions/cat" },
                { "$ref": "#/definitions/dog" }
            ]
        }
    }
}