Features of blockchain technology (BCT) such as decentralisation, trust, fault tolerance, and accountability, are of paramount importance for multi-agent systems (MAS). In this paper we argue that a principled approach to MAS-BCT integration cannot overlook the foundational character of agency—that is, autonomy. Accordingly, we present a custom BCT implementation where autonomy is placed in smart contracts (SC) interpreted as software agents. We show how agency can enhance SC expressiveness with autonomy, situatedness, sociality, and intelligence, and highlight the limitations of state-of-art BCT in supporting MAS design and implementation.