Code Runner MCP Server

0.1.8 · active · verified Sun Apr 19

The `mcp-server-code-runner` package provides a server designed to execute code snippets across a vast array of programming languages, including JavaScript, Python, PHP, Go, Ruby, TypeScript, and many others, then display their results. It acts as an MCP (Model Context Protocol) server, integrating with compatible AI clients and development environments like VS Code or Claude Desktop to offer real-time code execution capabilities. While the current version 0.1.8 suggests an early-stage or pre-1.0 development phase, it is actively maintained and serves as a powerful utility for agents requiring quick, sandboxed code execution. Its key differentiators include extensive language support (over 30 languages) and flexible deployment options via `npx` or Docker, making it highly adaptable for various AI-driven development and testing workflows.

Common errors

```
failed to start command: exec: "npx": executable file not found in $PATH
```
cause The `npx` command-line tool is not installed or not accessible in the system's PATH environment variable.

fix Install Node.js (which includes npm and npx) version 18 or later. Verify installation with `node -v` and `npx -v`. Ensure Node.js's installation directory is in your system's PATH.
```
Error: spawn npx ENOENT
```
cause The MCP client cannot correctly find the `npx` command in your system's PATH, often due to how child processes inherit environment variables, especially on Windows or with Node.js version managers like fnm.

fix Ensure `npx` is installed and the Node.js executable path is fully discoverable by the environment starting the MCP server. On Windows, try explicitly setting the `command` in your MCP server configuration to `cmd.exe` and passing `/c` before `npx` (e.g., `"command": "cmd.exe", "args": ["/c", "npx", "-y", "mcp-server-code-runner@latest"]`).
```
Cannot run program "C:\Program Files\nodejs\npx": CreateProcess error=193, %1 is not a valid Win32 application
```
cause This error can occur on Windows when the environment tries to execute `npx` in an incompatible mode (e.g., x86 on an x64 machine) or if the `npx` executable itself is corrupted or incorrectly linked.

fix Ensure your Node.js installation is correct for your system's architecture. Reinstall Node.js if necessary. Verify that no other Node.js tasks are interfering. Consider the `cmd.exe /c npx` workaround as described for 'spawn npx ENOENT' to ensure correct shell context.

Warnings

gotcha When running `mcp-server-code-runner` via `npx` on Windows, users may encounter issues related to PowerShell execution policies or `npx` not being found in the PATH, especially with Node.js version managers like nvm, fnm, or volta.
Fix: Adjust PowerShell execution policies (e.g., `Set-ExecutionPolicy RemoteSigned -Scope CurrentUser`). Ensure Node.js and `npx` are correctly installed and added to your system's PATH. For some environments, explicitly calling `cmd.exe /c npx ...` in the MCP server configuration might be necessary to ensure proper shell handling.
gotcha The server executes code locally on your machine. While powerful, this means executed code has potential access to your files or system resources. Running untrusted code without proper sandboxing can pose security risks, especially with AI agents.
Fix: Always use a reputable MCP client that prompts for explicit human confirmation before executing code. Consider running the server inside a Docker container for an isolated execution environment. Review the source code on GitHub for trusted servers.
gotcha To execute code in various programming languages, ensure that the respective language interpreter or compiler (e.g., Node.js for JavaScript, Python executable for Python) is installed and correctly configured in your system's PATH environment variable. The server relies on these external tools.
Fix: Verify that all necessary language runtimes are installed. Check your system's PATH environment variable to ensure the directories containing the interpreters/compilers are included. For Node.js, ensure version 18 or later is installed for optimal `npx` functionality.

Install

npm install mcp-server-code-runner npm
yarn add mcp-server-code-runner yarn
pnpm add mcp-server-code-runner pnpm

Imports

npx Command Invocation
wrong:
```
mcp-server-code-runner
```
correct:
```
npx -y mcp-server-code-runner@latest
```
This package is a server application, not a library meant for direct JS import. This entry describes the common command-line invocation pattern to run the server via npx. The `-y` flag is for automatic confirmation.

VS Code MCP Server Configuration

wrong:

{ "mcp-server-code-runner": { "command": "npx" } }

correct:

{
  "mcp": {
    "inputs": [],
    "servers": {
      "mcp-server-code-runner": {
        "command": "npx",
        "args": [
          "-y",
          "mcp-server-code-runner@latest"
        ]
      }
    }
  }
}

This JSON snippet illustrates how to configure the Code Runner MCP server within VS Code's `settings.json` to enable an AI agent to use it. The full `mcp` object structure is crucial.

Docker Invocation
wrong:
```
docker run formulahendry/mcp-server-code-runner
```
correct:
```
docker run --rm -i formulahendry/mcp-server-code-runner
```
This command demonstrates running the MCP server using Docker. The `--rm` flag ensures the container is removed on exit, and `-i` keeps stdin open. This provides an isolated execution environment.

Quickstart

This quickstart demonstrates configuring the `mcp-server-code-runner` within VS Code's `settings.json` to enable code execution capabilities for AI agents. This JSON structure registers the server to be run via `npx` on demand.

{
  "mcp": {
    "inputs": [],
    "servers": {
      "mcp-server-code-runner": {
        "command": "npx",
        "args": [
          "-y",
          "mcp-server-code-runner@latest"
        ]
      }
    }
  }
}

view raw JSON →