The enterprise software landscape is undergoing a foundational architectural shift that rivals the original transition from monolithic applications to distributed systems. For the past decade, the microservice architecture has successfully allowed engineering teams to manage application complexity through the strict decomposition of business domains into independently deployable, scalable units communicating over well-defined application programming interfaces (APIs). However, the aggressive integration of large language models (LLMs) into the application execution layer has catalyzed an entirely new paradigm: the agentic microservice architecture. In this advanced model, the core tenet of the single responsibility principle evolves from decomposing static business domains (such as an Order Service or a Payment Service) to decomposing dynamic cognitive loads (such as a Planner Agent, a Researcher Agent, and an Execution Agent).