Conversation Design has been gaining importance as a discipline in Customer Experience ever since conversations have been seen as a new type of user interface. Using voice and text, they result in stronger and more efficient relationships with people. At BBVA, we have co-created a Conversation Design System for Blue, our Smart Assistant. It allows us to keep its personality consistent in 4 countries and through 5 different channels, while establishing a flexible structure that helps UX Writers in each country to adapt our modular content to their language or linguistic particularities. By sharing our experiences building our system at a large scale company, I look forward to motivating AI enthusiasts to consider using similar Design Systems in their chatbot projects.