AgentKit is a LangChain-based starter kit to build constrained agent applications, offering a full-stack solution for rapid development, scalability, reliability, and user-centric design. It provides a framework for building agent-based applications with pre-defined Action Plans, a Router Agent, and tools that can be executed asynchronously. The platform prioritizes speed-to-value, keeping principles such as rapid development, modularity, and cognitive control in mind. With its configurability and modularity, AgentKit enables developers to build strong first proofs of concept quickly, scale applications to MVP, and ensure the reliability and safety of agent outputs.