This document discusses contested modelling approaches for sustainability interventions. It begins by noting that over-reliance on mathematical models has led to a loss of narrative and limited debate. It then examines different ontologies for understanding social-technical transitions, and questions whether modelling projects make their underlying ontologies explicit. The document also considers the purpose and enactment of modelling, and whether projects support reflexivity and stakeholder engagement. It analyzes several case studies along these dimensions and concludes by discussing challenges around validation and the need for wider stakeholder engagement in modelling to better support sustainability action.