We analyze how the rise of Generative AI (GenAI) has fundamentally changed marketing, arguing that rather than making the creative brief obsolete, it makes it even more crucial. The document emphasizes that AI requires a detailed and strategic brief as quality input to produce relevant and on-brand content, preventing the "garbage in, garbage out" problem. It highlights that the brief now acts as a strategic blueprint and ethical safeguard for AI execution, needing to evolve to include elements like prompt engineering guidance and ethical considerations. Ultimately, the text posits that the brief serves as the vital interface for effective human-AI collaboration in marketing.