Swagger Doc help adding a customProperty to a device

I don't typically use the /device/devices/{id}/properties/{name} endpoint but i would give the following a try:
 

    # Construct URL
        $resourcePath   = "/device/devices/2332/properties/Failover.Cluster.ParentGUID"
        $url            = $URLRoot + $resourcePath

        $data = `
@"
  {
        `"type`"         : `"custom`"                                    ,
        `"name`"         : `"Failover.Cluster.ParentGUID`"               ,
        `"value`"        : `"$ClusterID`"
  }
"@
        $response       = Send-Request  `
            -accesskey    $accessKey    `
            -accessid     $accessId     `
            -URL          $url          `
            -data         $data         `
            -httpVerb     "PUT"

The type key might not be needed. The SwaggerDoc on this endpoint is weird. It literally says that the POST method is supported but all the keys in the model are readOnly?