Dialogflow V2 always give this error:- Webhook call failed. Error: Webhook response was empty - integration

Question

I am trying to integrate my application with Dialogflow and Sending the request to Mulesoft and from there it is sending back the response in format mentioned in Webhook guide.
Below is the API request and response that is shown in Diagnostic info:-
Fulfillment Request:-
{
"responseId": "da851e5f-b6c3-4a17-bfdf-ad935d5003f6",
"queryResult": {
"queryText": "Open the report opportunity by Type where Type equals to New Customer",
"parameters": {
"reportName": "opportunity by Type",
"filterField": "Type",
"filterOperator": "equals",
"filterValue": "New Customer"
},
"allRequiredParamsPresent": true,
"fulfillmentText": "Displaying the report opportunity by Type where Type equals New Customer",
"fulfillmentMessages": [
{
"platform": "ACTIONS_ON_GOOGLE",
"simpleResponses": {
"simpleResponses": [
{
"textToSpeech": "Displaying the report opportunity by Type where Type equals New Customer"
}
]
}
},
{
"platform": "ACTIONS_ON_GOOGLE",
"simpleResponses": {
"simpleResponses": [
{
"textToSpeech": "Displaying the requested report on CRM"
}
]
}
},
{
"text": {
"text": [
"Displaying the report opportunity by Type where Type equals New Customer"
]
}
}
],
"intent": {
"name": "projects/sfdcconnect-68886/agent/intents/ef6d8d78-4dbf-4fb5-b647-4b427ca4dfa5",
"displayName": "show.report"
},
"intentDetectionConfidence": 1,
"languageCode": "en"
},
"originalDetectIntentRequest": {
"payload": {}
},
"session": "projects/sfdcconnect-68886/agent/sessions/4c9c3310-52ab-dbb5-73a8-b104ba55676e"
}
Fulfillment Response:-
{
"fulfillmentText": "This is a text response from Mulesoft",
"fulfillmentMessages": [
{
"card": {
"title": "card title",
"subtitle": "card text",
"imageUri": "https://assistant.google.com/static/images/molecule/Molecule-Formation-stop.png",
"buttons": [
{
"text": "button text",
"postback": "https://assistant.google.com/"
}
]
}
}
],
"source": "example.com",
"payload": {
"google": {
"expectUserResponse": true,
"richResponse": {
"items": [
{
"simpleResponse": {
"textToSpeech": "this is a simple response from Mulesoft"
}
}
]
}
},
"facebook": {
"text": "Hello, Facebook!"
},
"slack": {
"text": "This is a text response for Slack."
}
},
"outputContexts": [
{
"name": "projects/sfdcconnect-68886/agent/sessions/4c9c3310-52ab-dbb5-73a8-b104ba55676e/contexts/context name",
"lifespanCount": 5,
"parameters": {
"param": "param value"
}
}
],
"followupEventInput": {
"name": "event name",
"languageCode": "en-US",
"parameters": {
"param": "param value"
}
}
}
Under Raw API response:-
"webhookStatus": {
"code": 3,
"message": "Webhook call failed. Error: Webhook response was empty."
}
Fulfillment Status:-
Webhook call failed. Error: Webhook response was empty.
I have gone through multiple articles and validated that JSOn response is also correct. Also tried deleting the existing project and created a new one.
When testing this in Google actions, due to this error it is showing below error there as well:-
MalformedResponse
'final_response' must be set.
Is there any way to fix this error.
The action is being performed on Mulesoft end and response is being sent, it is just that it is not able to display the response under textToSpeech section to Google action/dialogflow.
Regards,
Rajat

Answer 1

The problem seems to be with the followUpEventInput / outputContexts, remove them as they're optional, or fill them properly.
WebHook Response Format