Developer Q&A

I'm trying to create a simple work order in sandbox using https://am-helper.corrigo.com/jll-wfs-sandbox/WoCreateCommand. The message returned is "{"type":"NullReferenceException","message":"Object reference not set to an instance of an object."}". It would be nice if the message was a bit more descriptive. Can anyone tell me what I need to change in my request?

{
"Region":"AM",
"commandRequest":{
"type":"WoCreateCommand",
"WorkOrder":{
"TypeCategory":"Request",
"SubType": {"Id":"259"},
"Customer": {"Id":"11"},
"Items":[{"Asset":{"Id":"26966"}, "Task":{"Id":"14099"}}],
"RequestorContact":{"Id":"25135"}
},
"ComputeSchedule":"false",
"ComputeAssignment":"false"
}
}