In this paper we propose a new software architecture for mobile agent toolkits. Agent toolkits mainly consist of a software system that forms an agency, which is responsible to host mobile and stationary software agents. In contrast to most architectures developed so far, which already define a large set of high-level services for agent migration and communication, we propose to employ a kernel-based approach. The kernel only provides fundamental concepts and functions and abstracts from any of these high-level services. We propose a new model for agencies and present our Tracy mobile agent toolkit acting as a reference implementation of our new model.