Unable to send custom payload via DialogFlow Fulfilment npm for Slack - node.js

Question

I am unable to send a custom payload back to dialogflow from my nodejs webhook code for SLACK platform.
const {WebhookClient, Payload, Platforms, Suggestion} = require('dialogflow-fulfillment');
let payloadObj = new Payload(Platforms.SLACK, questionStringToSend);
agent.add(payloadObj);
Here, questionStringToSend is the JSON payload that i want to send.
Any help would be appreciated.
Structure of my JSON is below:
{
"blocks":[
{
"type":"section",
"text":{
"type":"mrkdwn",
"text":"How do you rate the company?"
}
},
{
"type":"actions",
"elements":[
{
"type":"button",
"text":{
"type":"plain_text",
"text":0
},
"value":0
},
{
"type":"button",
"text":{
"type":"plain_text",
"text":1
},
"value":1
}
]
}
]
}

Answer 1

While sending a response from webhook the format of json is very important Link.
Custom payload response is a json file which has a specific structure and if the structure isn't followed we won't get the expected response.
So the json file can be edited as follows:
{
"fulfillmentMessages": [
{
"payload": {
"slack": {
"attachments": [
{"blocks":[
{
"type":"section",
"text":{
"type":"mrkdwn",
"text":"How do you rate the company?"
}
},
{
"type":"actions",
"elements":[
{
"type":"button",
"text":{
"type":"plain_text",
"text":"0"
},
"value":"0",
"action_id": "button"
},
{
"type":"button",
"text":{
"type":"plain_text",
"text":"1"
},
"value":"1"
}
]
}
]
}
]
}
}
}
]
}

Answer 2

try this
{
"blocks": [
{
"type": "section",
"text": {
"type": "mrkdwn",
"text": "How do you rate the company?"
}
},
{
"type": "actions",
"elements": [
{
"type": "button",
"text": {
"type": "plain_text",
"text": "0"
},
"value": "0"
},
{
"type": "button",
"text": {
"type": "plain_text",
"text": "1"
},
"value": "1"
}
]
}
]
}