Courier provides a single API call to send cross-channel notifications via Slack, MS Teams, and other channels from Node.js applications. To integrate with Slack, developers need to create a Slack app, add OAuth permission and scopes, and send a Slack DM with Node.js. For Microsoft Teams, they need to sign up for a Microsoft 365 developer account, create a Teams app, deploy the bot, install the bot, and add the Teams integration to Courier. Courier's multi-channel functionality allows sending notifications across multiple channels using a single API, making it easy to automate Slack and Teams notifications with Node.js. The platform also offers notification templates and automation tools for visual workflows.