The MESSIAHS project is investigating mechanisms that support task placement in heterogeneous, distributed, autonomous systems. MESSIAHS provides a substrate on which scheduling algorithms can be implemented. These mechanisms were designed to support diverse task placement and load balancing algorithms. As part of this work, we have constructed an interface layer to the underlying mechanisms. This includes the MESSIAHS interface language (MIL) and a library of function calls for constructing distributed schedulers. This article gives an overview of MESSIAHS, describes two sample interface layers in detail, and gives example implementations of well-known algorithms from the literature built using these layers.