Working developers everywhere now use AI tools, but most still struggle to turn prompts and prototypes into reliable software features. The Developer's Guide to AI teaches engineers how to build real, maintainable AI capabilities using the tools they already know-JavaScript, Python, APIs, vector search, and simple agent workflows without advanced math or machine learning. Readers learn where AI belongs in an application, how to design around real-world constraints like latency and cost, and how to avoid the brittle prototypes that fail under changing requirements. With clear examples and production-focused patterns, this book helps developers ship AI features that last.