Clojure REPL MCP server

This Clojure implementation of the Model-Channel Protocol (MCP) allows you to expose Clojure REPL functionality over Server-Sent Events (SSE) transport. It provides components for MCP communication while maintaining compatibility with Anthropic's MCP specification.

Installation

Add mcp-clj as a dependency to your Clojure project by including it in your dependencies:

:deps {org.hugoduncan/mcp-clj
        {:git/url   "https://github.com/hugoduncan/mcp-clj"
         :git/sha   "replace with latest git sha"
         :deps/root "projects/server"}}

Starting the Server

To start the MCP server in your project:

(require 'mcp-clj.mcp-server.core)
(def server (mcp-clj.mcp-server.core/create-server {:port 3001}))

This launches the server on port 3001, which you can then connect to using an MCP client.

Client Configuration

Setting Up Claude Desktop

To use Claude Desktop with the mcp-clj server, you'll need to configure it using mcp-proxy.

Add the following to your claude_desktop_config.json file:

"mcp-proxy": {
  "command": "mcp-proxy",
  "args": [
    "http://localhost:3001/sse"
  ],
  "env": {
    "API_ACCESS_TOKEN": "ABC"
  }
}

This configuration connects Claude Desktop to your local MCP server, allowing you to use the Clojure REPL functionality through the Claude interface.

How to add this MCP server to Cursor

There are two ways to add an MCP server to Cursor. The most common way is to add the server globally in the ~/.cursor/mcp.json file so that it is available in all of your projects.

If you only need the server in a single project, you can add it to the project instead by creating or adding it to the .cursor/mcp.json file.

Adding an MCP server to Cursor globally

To add a global MCP server go to Cursor Settings > MCP and click "Add new global MCP server".

When you click that button the ~/.cursor/mcp.json file will be opened and you can add your server like this:

{
    "mcpServers": {
        "cursor-rules-mcp": {
            "command": "npx",
            "args": [
                "-y",
                "cursor-rules-mcp"
            ]
        }
    }
}

Adding an MCP server to a project

To add an MCP server to a project you can create a new .cursor/mcp.json file or add it to the existing one. This will look exactly the same as the global MCP server example above.

How to use the MCP server

Once the server is installed, you might need to head back to Settings > MCP and click the refresh button.

The Cursor agent will then be able to see the available tools the added MCP server has available and will call them when it needs to.

You can also explictly ask the agent to use the tool by mentioning the tool name and describing what the function does.