Extending Mantle functionality with your own custom application
Mantle Extensions are user-built applications that are embedded (preferably) within Mantle, allowing developers to extend core Mantle functionality for their own needs (private), or to share with or sell to the community (public).
Embedded extensions are the preferred choice as they allow the user to provide a common look and feel in their application to make it feel part of the Mantle core product.
Non embedded extensions are for developers who do not have the ability to embed their application within the Mantle application (iframes) and must host the application in a full, separate, window.
It is important to remember, regardless of which type of extension you are building, before either session token or hmac authentication, you must perform the OAuth flow to get an access token if you have not done so already.