As the world continues to urbanize, identifying and implementing new urban development models and strategies is necessary to face sustainable development challenges. To this end, the circular economy model can be implemented in cities in order to operationalize and achieve human sustainable development managing simultaneously, in a systemic perspective, the social inequalities issue and the ecological and economic crisis. Today there are many cities that are defining themselves as a “circular city” but, to date, a clear definition of this does not exist. In the transition towards the circular city, tools (such as evaluation, governance, financial, business tools) play a fundamental role. The aim of this paper is (after an analysis of the concept of the circular city and its implementation, starting from literature, official documents and reports) to identify and analyze tools for implementing the circular city model. In particular, a set of indicators to assess (positive and/or negative) impacts of projects and initiatives of the circular city agenda is identified.