Error "Empty speech response"

Question

I tried to connect DialogFlow and Actions on Google, so I created some intents, connected the services, added explicit and implicit invocations etc, but when I try the bot in the simulator https://console.actions.google.com/project/[projectId]/simulator/ it always gives me the error:

"Failed to parse Dialogflow response into AppResponse, exception thrown with message: Empty speech response"

even tough inputType was "KEYBOARD".

What I tried so far:

• I did set "Response from this tab will be sent to the Google Assistant integration" in Dialog Flow (do you have to set it for every single intent?), but I don't see any extra setting for speech.
• I disabled the second language, first I had also intents in German
• I also turned off the Fullfillment Webhook (implemented in API v1 and then also v2) with no change
• I only found this user with the same problem https://productforums.google.com/forum/#!topic/dialogflow/xYjKlz31yW0;context-place=topicsearchin/dialogflow/Empty$20speech$20response but no resolution.
• the fulfillment checkbox is checked at the intents
• The bot works fine when I use it through "Try it now" on the very right in Dialog Flow or in the Web Demo https://bot.dialogflow.com/994dda8b-4849-4a8a-ab24-c0cd03b5f420

Unfortunately the docs don't say anything about this error. Any ideas?

Here a screenshot of the error on the Actions integration:

This is the full debug output:

{
  "agentToAssistantDebug": {
    "agentToAssistantJson": {
      "message": "Failed to parse Dialogflow response into AppResponse, exception thrown with message: Empty speech response",
      "apiResponse": {
        "id": "c12e1389-e887-49d4-b399-a332188ca946",
        "timestamp": "2018-01-27T03:55:30.931Z",
        "lang": "en-us",
        "result": {},
        "status": {
          "code": 200,
          "errorType": "success"
        },
        "sessionId": "1517025330705"
      }
    }
  },
  "assistantToAgentDebug": {
    "assistantToAgentJson": {
      "user": {
        "userId": "USER_ID",
        "locale": "en-US",
        "lastSeen": "2018-01-27T03:55:03Z"
      },
      "conversation": {
        "conversationId": "1517025330705",
        "type": "NEW"
      },
      "inputs": [
        {
          "intent": "actions.intent.MAIN",
          "rawInputs": [
            {
              "inputType": "KEYBOARD",
              "query": "Talk to Mica, the Hipster Cat Bot"
            }
          ]
        }
      ],
      "surface": {
        "capabilities": [
          {
            "name": "actions.capability.MEDIA_RESPONSE_AUDIO"
          },
          {
            "name": "actions.capability.WEB_BROWSER"
          },
          {
            "name": "actions.capability.AUDIO_OUTPUT"
          },
          {
            "name": "actions.capability.SCREEN_OUTPUT"
          }
        ]
      },
      "isInSandbox": true,
      "availableSurfaces": [
        {
          "capabilities": [
            {
              "name": "actions.capability.AUDIO_OUTPUT"
            },
            {
              "name": "actions.capability.SCREEN_OUTPUT"
            }
          ]
        }
      ]
    },
    "curlCommand": "curl -v 'https://api.api.ai/api/integrations/google?token=TOKEN' -H 'Content-Type: application/json;charset=UTF-8' -H 'Google-Actions-API-Version: 2' -H 'Authorization: AUTH_TOKEN'  -A 'Mozilla/5.0 (compatible; Google-Cloud-Functions/2.1; +http://www.google.com/bot.html)' -X POST -d '{\"user\":{\"userId\":\"USER_ID\",\"locale\":\"en-US\",\"lastSeen\":\"2018-01-27T03:55:03Z\"},\"conversation\":{\"conversationId\":\"1517025330705\",\"type\":\"NEW\"},\"inputs\":[{\"intent\":\"actions.intent.MAIN\",\"rawInputs\":[{\"inputType\":\"KEYBOARD\",\"query\":\"Talk to Mica, the Hipster Cat Bot\"}]}],\"surface\":{\"capabilities\":[{\"name\":\"actions.capability.MEDIA_RESPONSE_AUDIO\"},{\"name\":\"actions.capability.WEB_BROWSER\"},{\"name\":\"actions.capability.AUDIO_OUTPUT\"},{\"name\":\"actions.capability.SCREEN_OUTPUT\"}]},\"isInSandbox\":true,\"availableSurfaces\":[{\"capabilities\":[{\"name\":\"actions.capability.AUDIO_OUTPUT\"},{\"name\":\"actions.capability.SCREEN_OUTPUT\"}]}]}'"
  },
  "sharedDebugInfo": [
    {
      "name": "ResponseValidation",
      "subDebugEntry": [
        {
          "debugInfo": "API Version 2: Failed to parse JSON response string with 'INVALID_ARGUMENT' error: \": Cannot find field.\".",
          "name": "UnparseableJsonResponse"
        }
      ]
    }
  ]
}

Also "debugInfo" sounds like an internal problem:

"API Version 2: Failed to parse JSON response string with 'INVALID_ARGUMENT' error: \": Cannot find field.\"."

Here a screenshot of the welcome intent:

ps. It took me AGES to figure out, what

"Query pattern is missing for custom intent"

means - so I just document it here: In Dialog Flow - Intent - "User says" you have to DOUBLE CLICK on a word in the text input field when you want to set it as query parameter - which seems to be required for Actions on Google.

Answer 1

The Actions on Google support helped me fix this problem:

I needed to add a text as Default Response to the intent used for Explicit Invocation.