The webhook and API functions get triggered by events in external services such as GitHub, TFS, Office 365, OneDrive, and Microsoft PowerApps.

With the webhook and API functions, you can build notification Nanoservices that can perform custom operations whenever they receive a message on a configured webhook. For example, you can use webhooks with OneDrive that notifies your Nanoservice whenever a file gets uploaded to a folder.

Webhook and API functions accept a request and return a response. They mimic the web API or web service flows. These functions generally require some CORS (Cross-Origin Resource Sharing) settings to be managed. While developing the Nanoservices you can use an asterisk wildcard so they are wide open. However, you need to be aware that to invoke these Nanoservices from other services, you would need to set the cross-origin information in your function app settings.

These types of functions are generally used for exposing functionality to other apps and services. Other systems and clients can make web calls using HTTP protocols to them and expect a response. These Nanoservices are generally integrated with logic apps to form a workflow.