DM's Friend is a GPT that's been designed to aid Dungeon Masters (DMs) by providing expert knowledge on Dungeons & Dragons (D&D) rules. It operates as a specialised kind of chatbot, responding to user queries and offers rules clarification, explanations on various mechanics of gameplay, and general guidance to help enhance the D&D gameplay experience. The GPT operates by interpreting the nature of incoming queries and generating insightful, context-appropriate responses. The type of queries that it handles ranges from specifics like 'the right skill and ability check for when...' and the impact of specific spells, to clarifications on potential penalties and detailing the features of different game feats. DM's Friend is built to help users resolve rules queries in real-time, making it a handy companion and resource for DMs looking to make their gameplay sessions smoother and more enjoyable. It leverages the capabilities of chatbot technology to provide accessible, interactive, and instant expertise to the D&D community.