fsi
A wrapper around F# interactive (fsi) that exposes an MCP server endpoint for AI agents allowing for fsi IO.
claude mcp add --transport stdio jovaneyck-fsi-mcp-server dotnet run \ --env ASPNETCORE_URLS="http://0.0.0.0:5020"
How to use
FSI MCP Server provides a drop-in replacement for the F# Interactive (fsi.exe) workflow with integrated MCP capabilities. It runs as a .NET Core service and exposes MCP endpoints so your AI assistants or IDE integrations can send code, request status, and receive FSI events while you continue to use the standard FSI console. You can replace your FSI launcher with the fsi-mcp server and connect tools like Claude Code or GitHub Copilot to the server’s MCP API via the SSE/HTTP transport. The server is designed to intercept FSI input/output, relay it through MCP tooling, and maintain a shared REPL session that both you and your AI assistant can participate in. Basic usage starts with launching the server and pointing your tooling to http://localhost:5020 (or the configured URL).
How to install
Prerequisites:
- .NET SDK (recommended latest LTS)
- Basic familiarity with running command-line dotnet commands
Install steps:
- Clone the repository: git clone <repository-url> cd fsi-mcp-server
- Build the project: dotnet build
- Run the server (the server acts as a drop-in replacement for fsi, listening on port 5020 by default): dotnet run
- (Optional) Configure environment to expose the server on a specific URL or port: On Linux/macOS: ASPNETCORE_URLS=http://0.0.0.0:5020 dotnet run On Windows: set ASPNETCORE_URLS=http://0.0.0.0:5020 && dotnet run
- Verify the server is accepting connections at http://localhost:5020
Additional notes
Notes and tips:
- The server is a proof-of-concept and not yet production-ready.
- It provides MCP endpoints for sending F# code, loading scripts, and querying FSI status (e.g., GetRecentFsiEvents, GetFsiStatus).
- When integrating with IDEs or assistants, use the documented MCP transport (SSE/HTTP) endpoints as the source of truth for code execution in the FSI session.
- If you change the port or host, update all client configurations (Claude Desktop, Copilot prompts, etc.) to point to the new URL.
- Common issues often relate to port binding or missing dependencies; ensure ASPNETCORE_URLS is set correctly and that dotnet run completes build steps without errors.
