nREPL MCP Server

A Model Context Protocol (MCP) server designed for MCP clients, such as Claude Desktop or CLine in VSCode. This server can be used with any LLM when used with CLine. This server enables interaction with a running Clojure nREPL instance, allowing evaluation of Clojure code, namespace inspection, and other utilities via MCP.

Features

• Connect to a running nREPL server by specifying host and port.

• Evaluate Clojure code in a given namespace or the current one.

• List project namespaces using tools.namespace.

• Retrieve nREPL connection status, including host, port, and session details.

• Inspect public vars in any Clojure namespace, displaying metadata such as docstrings and values.

Related MCP server: Emacs MCP Tools

Installation & Setup

Installing in CLine (VSCode) or Claude Desktop

To use this server with CLine or Claude Desktop, follow these steps:

1. Open CLine in VSCode or Claude Desktop.

2. Navigate to the MCP Settings.

3. Add a new MCP server with the following configuration:

   {
     "mcpServers": {
       "nrepl-mcp-server": {
         "command": "npx",
         "args": [
           "nrepl-mcp-server"
         ],
         "disabled": false,
         "autoApprove": []
       }
     }
   }

4. Save and restart the client to apply changes.

This will allow the client to communicate with the nREPL MCP server via standard input/output.

Install via npx

To quickly run the server without cloning the repository:

npx nrepl-mcp-server

Manual Installation

1. Clone the repository

2. Install dependencies

   npm install

3. Build the project (transpiles TypeScript to JavaScript)

   npm run build

4. Run the server

   • Production Mode: Runs from compiled output.

     npm start

   • Development Mode: Uses ts-node for live changes.

     npm run dev

This starts the server, listening on STDIO for MCP requests. Mcp client will start the server for you.

Actions

Connecting to nREPL

Allows establishing a connection to an nREPL server by specifying a host and port.

Evaluating Clojure Code

Executes arbitrary Clojure expressions in either the default namespace or a specified namespace.

Retrieving Namespace Information

Lists all namespaces in the current project directory using tools.namespace.

Inspecting Public Vars

Fetches metadata and current values for all public vars in a specified namespace.

Fetching nREPL Connection Status

Provides details on the current nREPL connection, including host, port, session ID, and last error (if any).

Resources

nrepl://status

Provides information about the current nREPL connection, including:

• Host and port

• Connection status

• Active session ID

nrepl://namespaces

Lists all namespaces detected in the project directory.

Contributing

Contributions are welcome! If you have feature suggestions or bug reports, please open an issue or pull request.

License

This project is licensed under the MIT License. Feel free to modify and distribute according to its terms.