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

This response has no body data.