Start off by generating the App Secret and the Page Access token in Facebook Messenger.

1. Log into your Facebook developer’s account.

2. Create a Facebook page that hosts your bot. The description, images, and cover page you add to the page will identify your bot to its users.

3. Next, create the Facebook app that you’ll link to this page. Because this is a Messenger app, choose Apps for Messenger and then click Create App ID.
   
   
   

   If you didn't choose the Apps for Messenger option in this dialog (for example, if you’re creating a test app), then click Add Product in the left navbar, choose Messenger from the Product Setup page, and then click Get Started.
   
   
   

4. On the Dashboard page of the Facebook app, copy the app secret and paste somewhere convenient on your system.
   
   
   

   You’ll need the app secret to complete your Facebook channel configuration.

5. In the Dashboard for your app, generate the Page Access Token by selecting your Facebook page.
   
   
   

6. Copy the access token and paste it somewhere convenient.

   You’ll use this token, which gives your Facebook App access to Facebook’s Messaging API, to complete your channel definition in Digital Assistant.

With the configuration complete, you’re ready to activate the Facebook channel.

• In Digital Assistant, select the channel and switch on the Channel Enabled control.
• Click and select the digital assistant or skill that you want to associate with the channel.

You can now test the bot through the channel.

With the Facebook Channel and messaging configuration complete, you can test your bot using your Facebook page, Facebook Messenger (https://www.messenger.com/) and the Facebook Messenger app on your phone (). Once you locate your bot in the search, you’re ready to start chatting with it. You can see the changes that you make to the dialog flow in real time.

Facebook Messenger enables you to create a persistent menu next to its Message field. See https://developers.facebook.com/docs/messenger-platform/send-messages/persistent-menu/ for details on the feature.

Here's an example that shows persistent menu items for "Order Pizza" and "Order Pasta":

Facebook Messenger channels in Digital Assistant support the following capabilities:

• text (both sending and receiving)
• images (both sending and receiving)
• files (both sending and receiving)
• emojis (both sending and receiving)
• location, but deprecated (both sending and receiving)
• links
• postbacks
• location requests
• custom properties
• carousel components
• list components

If you are targeting your skill to multiple channels with different formatting capabilities and syntax, you can use basic HTML markup in your messages. If you do so, that markup will be automatically converted to Facebook Messenger's markdown format when the message is transmitted to the channel. This is particularly useful if you are targeting your skills to other channels in addition to Facebook Messenger. See Rich Text Formatting in Channels.

Facebook Messenger channels in Digital Assistant have the following message constraints:

• Text Messages
  • Maximum length of text message: 640 characters. If the length exceeds 640, the text is split over multiple messages.
  • Maximum length of text action label: 20 characters
  • Types of text actions allowed: Postback, Call, URL
  • Maximum number of text actions: 3. If there are more text actions, the message is converted to multiple horizontal cards, with the same text used as the title on each card, and each card containing up to 3 actions.
• Horizontal Cards
  • Maximum length of title: 80 characters
  • Maximum length of description: 80 characters
  • Maximum length of card action label: 20 characters
  • Maximum number of cards: 10
  • Maximum number of card actions: 3. If the number of card actions exceeds 3, the card is duplicated to render remaining card actions.
  • Minimum number of card actions: 0
  • Maximum number of card list actions: 0
  • At least one description, image or action required?: Yes
  • Types of card actions allowed: Postback, Call, URL, Share
  • Types of card list actions allowed: N/A
• Vertical Cards
  • Not supported
• Attachment Messages
  • Supported?: Yes
  • Attachment actions allowed?: No
• Action Buttons
  • Maximum length of global action label: 20 characters
  • Maximum number of global actions: 11
  • Types of global actions allowed: Postback

For Facebook Messenger channels, you can extend the functionality of Common Response components with capabilities that are specific to Facebook.

You access the extensions by using the channelCustomProperties element in the Common Response component's metadata and setting the appropriate properties. The code has the following format:

...
            channelCustomProperties:
            - channel: "facebook"
              properties:
                PROPERTY_NAME: "PROPERTY_VALUE"
...

Here are the available custom properties for Facebook Messenger channels:

Here is an example of custom properties defined at the response item level (top_element_style) and the cards level (webview_height_ratio and fallback_url):

responseItems:
  - type: "cards"
    cardLayout: "vertical"
    cards:
      - title: "${pizzas.name}"
        description: "${pizzas.description}"
        imageUrl: "${pizzas.image}"
        url: "${pizzas.moreInfo}"
        iteratorVariable: "pizzas"
        channelCustomProperties:
          - channel: "facebook"
            properties:
              webview_height_ratio: "compact"
              fallback_url: "http://www.oracle.com"
    channelCustomProperties:
      - channel: "facebook"
        properties:
          top_element_style: "large"
...

For more general information on channelCustomProperties, see Channel-Specific Extensions.