We provide two libraries that can help you build a fulfillment webhook using Node.js.
For agents with multiple integrations
The Dialogflow Fulfillment Library is designed to assist with building a fulfillment webhook. The library simplifies generating rich messages for multiple integrations including Google Assistant, Slack, Facebook, Telegram, Kik, Skype, Line, and Viber.
To see an example of the Dialogflow Fulfillment Library in use, take a look at Dialogflow Fulfillment Webhook Template for Node.js.
For agents built solely for the Google Assistant
If you are building an agent solely for the Google Assistant and do not need to support any other integrations, you can use the Actions on Google Client Library, which provides advanced support for Actions on Google platform features.