Anonymous credential systems are a key ingredient for a secure and privacy protecting electronic world. In their full-fledged form, they can realize a broad range of requirements of authentication systems. However, these many features result in a complex system that can be difficult to use. In this paper, we aim to make credential systems easier to employ by providing an architecture and high-level specifications for the different components, transactions and features of the identity mixer anonymous credential system. The specifications abstract away the cryptographic details but they are still sufficiently concrete to enable all features. We demonstrate the use of our framework by applying it to an e-cash scenario.