GNU Taler must be usable for non-expert customers including end-users of a GNU Taler wallet, merchants who wish to accept payments using GNU Taler, and 3rd party application developers for e-commerce and other platforms. GNU Taler must follow best-practices usability guidelines and incorporate feedback from experts and users. Free/Libre software also requires Free/Libre documentation to allow for informed choices. GNU Taler must provide well-documented Application Programming Interfaces (APIs) to allow frictionless integrations between GNU Taler and other projects.