curl --request POST \
  --url https://api.hubapi.com/automation/v4/actions/callbacks/{callbackId}/complete \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "outputFields": {},
  "typedOutputs": {},
  "failureReasonType": "<string>",
  "requestContext": {
    "source": "WORKFLOWS",
    "workflowId": 123,
    "actionId": 123
  }
}
'

This response has no body data.