mcp-nrepl

An MCP (Model Context Protocol) server that connects to nREPL servers, enabling AI assistants like Claude to evaluate Clojure code interactively.

Overview

This server provides a bridge between MCP-compatible clients and nREPL, the standard network REPL protocol used in Clojure development. It allows AI assistants to connect to running Clojure processes and evaluate code in real-time.

Features

• Connect to any nREPL server by host and port
• Evaluate Clojure code and return results
• Seamless integration with Claude Desktop and other MCP clients

Requirements

• Python 3.13 or higher
• PDM (Python package manager)
• A running nREPL server to connect to

Installation

pdm install
ln -s $(pdm run which mcp-nrepl) ~/.local/bin/

If ~/.local/bin is not in your PATH, add the following to your shell configuration:

export PATH="$HOME/.local/bin:$PATH"

Configuration

Claude Desktop

Add the following to your claude_desktop_config.json:

{
  "mcpServers": {
    "nrepl": {
      "command": "mcp-nrepl"
    }
  }
}

Usage

Once configured, the MCP server provides an action_nrepl tool that accepts:

• host: The nREPL server hostname
• port: The nREPL server port
• code: The Clojure code to evaluate

The tool connects to the specified nREPL server, evaluates the code, and returns the result.

Development

Run the server in development mode:

pdm run mcp-nrepl

NixOS Users

If PDM fails with a missing virtualenv error, configure it to use the built-in venv module instead:

pdm config venv.backend venv

See NixOS/nixpkgs#225730 for more details.

License

Apache-2.0