JSON ERROR PE231

I have the following custom script:

$connection = Connect-VIServer -Server xxx.xxx.xxx.xxx -User xxxx -Password xxxx

Write-Host "<prtg>"

ForEach ($VM in Get-VM | where-object {($_.powerstate -ne "PoweredOff") }){


ForEach ($Drive in $VM.Extensiondata.Guest.Disk) {
    
    $Path = $Drive.DiskPath

    #Calculations 
    $Freespace = [math]::Round($Drive.FreeSpace / 1MB)
    $Capacity = [math]::Round($Drive.Capacity/ 1MB)

    $PercentFree = [math]::Round(($FreeSpace)/ ($Capacity) * 100) 

    #VMs with less space

    if ($PercentFree -lt 20) {     

      $message = "$VM $Path"

      Write-Host "<result>"

      Write-Host "<channel>$message</channel>"

      write-host "<LimitMinWarning>20</LimitMinWarning>"

      write-host "<LimitMinError>10</LimitMinError>"

      Write-Host "<LimitMode>1</LimitMode>"

      Write-Host "<value>$PercentFree</value>"

      Write-Host "<unit>Percent</unit>"

      Write-Host "</result>"     

    }

} 


} 

Write-Host "</prtg>"

An if I try to use it as a sensor I get a JSON error.

error json powershell script