Change cluster tier through admin APIs

Hello,
I’d like to change a dedicated cluster’s tier, e.g., from M20 to M10, through the admin APIs.
However, I’m not able to write a proper request payload.

I’m using the PATCH method with the URL
https://cloud.mongodb.com/api/atlas/v2/groups//clusters/
clearly by setting the proper ID and NAME.

I get always:
“errorCode”: “INVALID_JSON_ATTRIBUTE”,

I tried with this body:

{
    "replicationSpecs": [
        {
            "regionConfigs": [
                {
                    "analyticsAutoScaling": {
                        "compute": {
                            "maxInstanceSize": "M10",
                            "enabled": true,
                            "scaleDownEnabled": false
                        },
                        "diskGB": {
                            "enabled": true
                        }
                    },
                    "analyticsSpecs": {
                        "instanceSize": "M10",
                        "diskSizeGB": 51.0,
                        "nodeCount": 0
                    },
                    "autoScaling": {
                        "compute": {
                            "maxInstanceSize": "M10",
                            "enabled": true,
                            "scaleDownEnabled": false
                        },
                        "diskGB": {
                            "enabled": true
                        }
                    },
                    "electableSpecs": {
                        "instanceSize": "M10",
                        "diskSizeGB": 51.0,
                        "nodeCount": 3
                    },
                    "readOnlySpecs": {
                        "instanceSize": "M10",
                        "diskSizeGB": 51.0,
                        "nodeCount": 0
                    }
                }
            ]
        }
    ]
}

Do you have any advice?

Thanks, Andrea