Developers can create bot in Mixin messenger. Bot can receive payment and send asset to user. Bot can accept text, sticker, image from users and send many contents to users. Messenger user can not directly transfer asset to bot. Bot can create payment link and send link to user so user can click link to pay. User can visit bot's website inside messenger application.
When messenger user send text or sticker to bot in messenger application, Mixin messenger server will forward the message to bot. When messenger user pay to bot, Mixin messenger server will send notification to bot. To receive the notification and message, developer need to setup a WebSocket client. The client need to connect to Mixin messenger server, then receive all unread messages and notifications. After accepting message and notification, client need to send response to server so it know message is delivered correctly.
Developer also need to setup a web server and fill the web server address in developer dash board. The server will be visited when messenger user click robot icon.
Many security parameters will be generated by developer dash board. These parameter are required in most of API call.
A tutorial can help you learn Mixin Network.