JSON pointer to elements in arrays of non-fixed length

[unext-wendong]

Kindly let me know if this is the wrong place to ask this question.

Given the following sample schema, property Services is an array of non-fixed length.

{
    "definitions": {
        "Service": {
            "properties": {
                "Id": {
                    "description": "The ID of the service instance.",
                    "type": "string"
                },
                "Type": {
                    "description": "The type of the service instance.",
                    "type": "string"
                }
            },
            "additionalProperties": false
        }
    },
    "properties": {
        "Id": {
            "description": "Unique identifier.",
            "type": "string"
        },
        "Services": {
            "description": "The list of services.",
            "type": "array",
            "items": {
                "$ref": "#/definitions/Service"
            }
        }
    },
    "additionalProperties": false,
    "readOnlyProperties": [
        "/properties/Id"
    ],
    "primaryIdentifier": [
        "/properties/Id"
    ],
    "writeOnlyProperties": [
        "/properties/Services/0/Id"
    ]
}

How could I express in the schema that the Id property in the Service data is write-only? I mean what json pointers should I put in writeOnlyProperties.

If the Services array is of fixed length, I could list all /properties/Services/0/Id, /properties/Services/1/Id, ..., there, but it's of non-fixed length.

If it's not possible, is there any other way to express this?

Thanks,