Deep dive into OAuth 2.1 and MCP using Cloudflare Workers

Setting up a Model Context Protocol (MCP) server provides a streamlined method for AI applications like Claude, Gemini, and ChatGPT to interact with various products through function calls. This blog post describes the process of building an MCP server using a Cloudflare Worker, focusing on creating a basic server with a calculator tool capable of performing arithmetic operations. Key steps include configuring the server with necessary dependencies, setting up authentication and authorization using OAuth 2.1 via PropelAuth, and ensuring security by validating client credentials and consented scopes. The server is tested with Claude Desktop, demonstrating the workflow of requesting and processing tool calls. This setup not only facilitates basic operations like calculations but can be extended to more complex real-world applications, such as querying SEO data or managing calendar events, by integrating with existing APIs.