使用dialogflow Webhook时不显示Google操作卡

Question

我正在使用Dialogflow V1和webhooks构建Google Action。我的webhook返回以下JSON，但该卡未显示在模拟器或手机的Home应用中。

    {
    "conversationToken": "[]",
    "expectUserResponse": true,
    "expectedInputs": [{
        "inputPrompt": {
            "richInitialPrompt": {
                "items": [{
                        "simpleResponse": {
                            "textToSpeech": "I have some recipes which contain alcohol. Are you over 21? "
                        }
                    },
                    {
                        "basicCard": {
                            "title": "Lemonade Classic",
                            "formattedText": "The Lemonade Classic is the perfect companion for warm summer days.",
                            "image": {
                                "url": "https://s3-us-west-2.amazonaws.com/sparklingice/Mobile/Lemonade%20Classic_Mobile_336x192.png",
                                "accessibilityText": "accessability text"
                            }
                        }
                    }
                ]
            }
        }
    }],
    "responseMetadata": {
        "status": {
            "message": "Success (200)"
        }
    },
    "speech": "<speak>I have some recipes which contain alcohol. Are you over 21? </speak>",
    "displayText": "I have some recipes which contain alcohol. Are you over 21? ",
    "source": "My Bot"
}