The Open & Agile Smart Cities (OASC) network defines Minimal Interoperability Mechanisms (MIMs) as a set of essential, lightweight enablers that ensure a minimal yet sufficient level of interoperability between data, systems, and services within the context of smart city solutions. A MIM offers practical and easy-to-use approaches, encompassing both technical and non-technical solutions, to facilitate seamless collaboration and integration across cities and platforms.