For aspiring start-up entrepreneurs, developing their Business Model Canvas (BMC) well is key to their future success. Errol is an interactive agent that aims to play the role of a teacher who can provide feedback on users’ BMCs. Using some heuristics and applying these through the methods of lexical and semantic analysis, Errol poses questions to users based on their BMCs. Users can then think about the answers to these questions and update their BMCs accordingly. And on an even more general scale, we can say that Errol may be a way to develop theories on how humans make errors and what we can do to fix those.