prairiedog2k/fpc-mcp-server

This repository provides a reusable server for projects built with Free Pascal and Lazarus, two tools for writing Pascal applications. The server implements something called the Model Context Protocol, or MCP, which lets an application expose its own tools to a client program like Claude Code. The code was originally written for a specific project involving Cheat Engine, then pulled out into this standalone package so other Pascal applications can use it without rebuilding the underlying plumbing. The server handles the communication layer. It runs an HTTP server, frames messages using JSON-RPC, manages sessions between client and server, dispatches tool requests to the right handler, and can run longer tasks in the background as async jobs. An application that wants to offer tools to an MCP client only needs to register its own tool functions. The repository includes a small example program called echo_server that registers a single tool which simply sends back whatever text it receives. This example proves the full round trip works, from client request to server response. Building the project requires Lazarus and the Free Pascal Compiler, tested on Windows 64-bit. The build process uses standard Pascal library units for HTTP and JSON handling, so no extra packages are needed. The server code uses Windows-specific networking APIs, which means this project currently runs only on Windows. That limitation comes from the Cheat Engine fork it was originally extracted from. To extend the server, an application calls a registration function from its own code to add a new tool. It can also set the server name and version, and optionally associate each session with a target identifier such as a process ID. The repository organizes its code into several units: one for the HTTP server, one for JSON-RPC handling, one for the tool registry, one for session objects, one for async job handling, one for result formatting, and one for running tasks on the main thread. The tool registry is the main extension point where applications plug in their own functionality.