Swagger Doc help adding a customProperty to a device

Thank you Joe, looks like the JSON was the part I had wrong!  This worked for making the new property and populating it:

        $resourcePath   = "/device/devices/2332/properties/"
        $url            = $URLRoot + $resourcePath

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