Describing object's keys with MSON

Question

I have API that looks like this.

The products object contains Product IDs (keys) and their amount in basket (values).

{
    "id": "0a4d44aa-2ace-11e7-93ae-92361f002671",
    "products": {
        4 => 3, // product with ID 4 is 3x in basket
        10 => 1, // product with ID 10 is 1x in basket
        ...
    },
    // some other values...
}

a) How can I describe this API with MSON?

b) Is this schema correct?

{
    "type": "object",
    "properties": {
        "id": {
            "type": "string",
        },
        "products": {
            "type": "object",
            "properties": {
                 "productId": {
                     "type": "int",
                 }
            }
        },
        // some other values
    }       
}