This paper is dedicated to the issue of structural performance of multi-agent platforms. Due to the wide range of all available architectures, we have concentrated only on Java RMI implementations. The main goal of this paper consists of two parts. The first one is to investigate and develop the performance metrics to enable evaluation of distributed systems without reorganization of the running system. The second part is the programming verification of two considered Java RMI multi-agent solutions: Aglets and Jade. We have examined the defined metrics in many experiments with different network and environment configurations to provide experimental evidence that these metrics are adequate in variety of conditions.