gtmresponse.js

// REQUEST BODY IN API EXPLORER

{
  "accountId": "526400647",
  "containerId": "2678459",
  "name": "trigger1",
  "type": "customEvent",
  "triggerId": "3",
  "eventName": {
    "key": "eventName",
    "value": "whateverEvent",
    "type": "template"
  },
}

// RESPONSE SHOWN BELOW

{
 "error": {
  "errors": [
   {
    "domain": "global",
    "reason": "invalidArgument",
    "message": "Bad Request"
   }
  ],
  "code": 400,
  "message": "Bad Request"
 }
}