With circular economy being high on governmental agendas, there is an increasing request from governing bodies for circularity measurements. Yet currently existing macro-level monitoring frameworks are widely criticized for not being able to inform the decision making. The reasons behind their failure stem from a lack of consensus on terminologies and definitions among scholars, politicians and practitioners, a lack of supporting data and tools and, consequently, a lack of transparency and trustworthiness.To fulfill those needs, a bottom-up approach to build a shared terminology is suggested by involving macro-framework users within a government, data providers and tool developers. Their expertise and expectations for monitoring the transition are elicited through the process of formal ontology development and alignment.The ontology development experiment builds upon a use case of the Amsterdam Circular Economy Monitor (2020). First, four ontology development approaches are used to create a theory-centered, a user-centered, a tool-centered and a data-centered ontology. The ontologies are later compared, merged, and aligned with each other to arrive at one single ontology. The notes taken during the process are used to provide a detailed discussion on common concepts, identified conflicts, and gaps in monitoring expectations between the monitor users, data, tools, and the latest theory.