Engineering MCP tools for token efficiency

Writing an MCP server can be a rewarding experience, especially when it seamlessly integrates with tools like Claude and showcases its capabilities through the Model Context Protocol (MCP), which standardizes the way external services are made available to agents. The use of libraries such as rmcp in Rust, or custom libraries like mercutio, can simplify the implementation process by abstracting protocol specifics. The article explores using Open-Meteo for weather data, emphasizing the importance of efficient data transformation for presentation. It discusses the benefits of snapshot testing in Rust, which helps capture and verify output, ensuring consistency and clarity in results. The importance of optimizing the context window in large language models (LLMs) is highlighted, as it impacts the effectiveness of the tool. The piece concludes by advocating for strategies like simplifying API interfaces and using examples to reduce token usage, thus enhancing the interaction with LLMs.