Behind the scenes of every chatbot and conversational artificial intelligence (AI) system is the labor of conversation designers, whose work lies somewhere between the application of user experience principles and the art of script writing. Conversation designers construct the voices and polish the tone that gives these tools a personality (or tries to avoid one). Based on ongoing fieldwork at a Japanese Conversational AI startup, I discuss how one team of conversation designers is shaping a GPT-based tool to help measure students’ English language competency and help them practice without self-consciousness. This project has recently gotten a lot of attention in the Japanese press, but those who tell its story frequently forget about the contribution of anyone except the engineers- especially the linguists, psychologists, and teachers who are this tool’s voice.