The System Designer tool acts as a Model Context Protocol (MCP) server, equipping AI agents with a powerful set of capabilities for system design and application generation. It enables the comprehensive creation, validation, and export of UML system models using MSON (Metamodel JavaScript Object Notation) and facilitates the generation of complete, executable System Runtime bundles. Utilizing a tool-based architecture, System Designer empowers large language models (LLMs) to construct sophisticated applications by handling the understanding of requirements, while the server ensures robust validation, type safety, and seamless integration with the System Designer macOS application.