schema.json

{
    "$schema": "http://json-schema.org/draft-07/schema#",
    "additionalProperties": false,
    "definitions": {
        "MyGeneric<number,string>": {
            "additionalProperties": false,
            "properties": {
                "a": {
                    "type": "number"
                },
                "b": {
                    "type": "string"
                }
            },
            "required": [
                "a",
                "b"
            ],
            "type": "object"
        },
        "MyGeneric<string,number>": {
            "additionalProperties": false,
            "properties": {
                "a": {
                    "type": "string"
                },
                "b": {
                    "type": "number"
                }
            },
            "required": [
                "a",
                "b"
            ],
            "type": "object"
        }
    },
    "properties": {
        "value1": {
            "$ref": "#/definitions/MyGeneric<string,number>"
        },
        "value2": {
            "$ref": "#/definitions/MyGeneric<number,string>"
        }
    },
    "required": [
        "value1",
        "value2"
    ],
    "type": "object"
}