Dialogflow V2 API says my Webhook response was empty - google-api

Question

I am trying to use the Dialogflow V2 API to add two numbers, to do this I have setup a web server with HTTPS access to complete the request. in the Diagnostic Info screen in the Dialogflow console I can see the Fulfilment Response from my remote server:
{
"fulfillmentText": "the sum of 5 and 9 is 14",
"fulfillmentMessages": [
{
"text": {
"text": [
"the sum of 5 and 9 is 14"
]
}
}
],
"source": "-------.com",
"payload": {
"google": {
"expectUserResponse": 1,
"richResponse": {
"items": [
{
"simpleResponse": {
"textToSpeech": "the sum of 5 and 9 is 14"
}
}
]
}
},
"facebook": {
"text": "the sum of 5 and 9 is 14"
},
"slack": {
"text": "the sum of 5 and 9 is 14"
}
},
"outputContexts": [
{
"name": "-----892446d1-----",
"lifespanCount": 1,
"parameters": {
"number": 5,
"number1": 9
}
}
]
}
Which has been adapted from the example given in the docs: https://dialogflow.com/docs/intro/fulfillment but in the Raw API response I see:
"webhookStatus": {
"code": 3,
"message": "Webhook call failed. Error: Webhook response was empty."
}
Clearly the response is not empty as it can be seen in the Diagnostic Info. Has anyone any ideas as to what is causing this?
Thanks

Answer 1

We can find definition of the codes in google.rpc package error codes,
"code": 3
means "INVALID_ARGUMENT"
// The client specified an invalid argument. Note that this differs
// from FAILED_PRECONDITION. INVALID_ARGUMENT indicates arguments
// that are problematic regardless of the state of the system //
(e.g., a malformed file name).
For example according to request format "parameters" field in "outputContexts" should have format "param": "param value", in your request it looks like "param": param value.
Please check all arguments in your request.