SWIS Verb Arguments

Hello! I'm working to add  a note to an Alert via the Powershell SWIS SDK. Here's the relevant line That I'm using:

$noteResult = (Invoke-SwisVerb $swis "Orion.AlertStatus" "AddNote" @($myAlert,$MessageText)).ChildNodes.Value   

The problem is that it apparently needs 4 arguments, not 2. Where can I find the arguments required?

Invoke-SwisVerb : Verb Orion.AlertStatus.AddNote requires 4 parameters not 2