REST API payload format error with 500 response

Hi all,

I have created an integration definition with the script include where it calls to action and returns payload, and this integration definition is used in a flow. 

When I test the flow with RITM it returns error 500 saying "Method failed: (/v1/device-type) with code: 500" I have checked the endpoint URL and everything seems right. The only issue might be the payload format. Currently this is the payload format

{
    "id": "testDeviceType102",
    "friendlyName": "friendlyName",
    "description": "description",
    "manufacturer": "Test",
    "type": "General purpose",
    "deviceClass": "CLASS_A",
    "associatedphysicalDeviceType": "tektelicLns"
}

Does anyone know what might be the issue with the format?