As Generative AI shifts from simple retrieval to autonomous action, enterprises face the engineering challenge of scaling scattered proofs of concept into robust, secure systems. This article deconstructs the architecture of a production-grade AI Agent Platform, positioning it as an internal Platform-as-a-Service (PaaS) that supports both code-first engineers and low-code integrators. By breaking the system down into seven logical containers—Interaction, Development, Core, Foundation, Information, Observability, and Trust—the guide outlines a blueprint for a “factory” capable of serving, securing, and monitoring a fleet of agents that deliver tangible business ROI.