As businesses increasingly explore building AI agents, this guide provides a structured approach for developing such agents from concept to impact, using the example of building an email agent. It outlines a six-step framework starting with defining the agent's job through realistic examples, followed by designing a detailed operating procedure to ensure the problem scope is manageable. The process continues with building a minimum viable product (MVP) focusing on the most critical reasoning tasks, and then connecting the MVP to real data using orchestration logic. The guide emphasizes the importance of testing and iterating to refine the agent's performance before deployment, and it highlights the necessity of continuous monitoring and adaptation based on user feedback and real-world usage patterns. Ultimately, the guide stresses that launching an agent is just the start of an iterative process to ensure the agent remains useful, reliable, and aligned with user needs.