Enhancing research synthesis by documenting intervention development decisions: Examples from two behavior change frameworks Marta M. Marques, Gjalt-Jorn Y. Peters To support the development of behaviour change interventions, there is a considerable amount of guidance (e.g. Intervention Mapping) on how to select behaviours, identify behavioural determinants, and select methods/techniques. When it comes to decisions about which modes of delivery are best for certain methods, and how they should be designed, there is little guidance. While researchers make these decisions during the development of interventions, these decisions are not well documented, and as such, opportunities to learn from the justifications of those decisions are lost. An easily usable, systematic, efficient and machine-readable approach to reporting decisions and justifications of such decisions would improve this situation and enable accumulation of the knowledge that at present remains largely implicit. We introduce ‘justifier’, an R package that allows reading and organizing fragments of text that encode such decisions and justifications. By adhering to a few simple guidelines, the meeting minutes and documentation of the intervention development process become machine-readable, enabling aggregation of the decisions and their evidence base over one or multiple intervention development processes. Tools such as heatmaps can be used to visualise these patterns, quicky making salient where decisions were based on higher and lower quality evidence. We present two hierarchical compilations of the key decisions to justify during intervention development, one based on the Behavior Change Wheel procedure and one based on the Intervention Mapping protocol. Using the proposed ‘justifier’ format document the decisions and their justifications in these key domains provides greater insight in the intervention development process.