ROOT MCP Server

---

Minimal MCP (Model Context Protocol) server that allows LLMs and other MCP clients to execute Python and C++ code directly using PyROOT, without HTTP endpoints or external APIs.

Features

• Direct Python execution: Run Python code with PyROOT available automatically
• Direct C++ execution: Run C++ code via ROOT's cling interpreter
• In-process: All code runs in the same process (no subprocess isolation)
• Error detection: Automatic detection of C++ compilation errors via return codes and stderr
• Console logging: Pretty-printed code execution with results in MCP console
• Graphics support: TCanvas and ROOT graphics objects with event loop support

Architecture

Below is the architecture diagram for the root_mcp_server project. The image contains a visual representation of the components and their interactions.

Description:

• MCP Client (VS Code / CLI / Programmatic): connects to the MCP server and sends execution requests. Clients can be interactive (e.g. VS Code + Copilot Chat) or scripted CLI clients.
• FastMCP Server: receives MCP tool calls (root_python, root_cpp) and dispatches them to the in-process executor.
• RootExecutor (in-process PyROOT): runs Python or C++ code with the ROOT runtime, manages graphics mode, and can expose an embedded HTTP server (THttpServer) for interactive canvases.
• ROOT Web Canvas (THttpServer / JSROOT): when graphics are enabled, canvases created in the ROOT session are available via the embedded HTTP server; clients can open the provided URL to inspect plots interactively.
• Artifacts & Outputs: execution results (stdout/stderr and error metadata) are returned to the MCP client; interactive canvases are accessible via the HTTP endpoint.

This architecture keeps ROOT running in-process for low-latency execution while providing a web-backed path for interactive visualization.

Installation

Prerequisites

• ROOT (6.x or later) with PyROOT enabled
• Python 3.10+

Install the package

pip install -e .

Usage

Option 1: VS Code with GitHub Copilot Chat

The easiest way to use this MCP server is through VS Code with GitHub Copilot Chat.

1. Install GitHub Copilot Chat extension

Make sure you have the GitHub Copilot Chat extension installed in VS Code.

2. Configure MCP server in VS Code

Add the MCP server configuration to your VS Code settings. Open your settings.json (Ctrl/Cmd + Shift + P → "Preferences: Open User Settings (JSON)") and add:

{
  "github.copilot.chat.codeGeneration.instructions": [
    {
      "text": "Use ROOT MCP server for data analysis"
    }
  ],
  "mcp.servers": {
		"root/mcp-server": {
			"type": "stdio",
			"command": "root_mcp_server",
			"args": []
		}
  }
}

Important: Replace /path/to/ROOT/build/bin/thisroot.sh with the actual path to your ROOT installation's thisroot.sh script.

3. Use in Copilot Chat

Once configured, you can use the MCP tools in GitHub Copilot Chat:

@workspace Use #root_python to execute Python code with PyROOT

@workspace Use #root_cpp to execute C++ code with ROOT

The server will automatically log executed code and results to the MCP console (visible in VS Code's Output panel).

Option 2: Command line

Start the MCP server directly:

root_mcp_server

Option 3: Programmatic usage

from mcp.client.stdio import stdio_client, StdioServerParameters
from mcp.client.session import ClientSession

server_params = StdioServerParameters(
    command="bash",
    args=["-lc", "source /path/to/thisroot.sh && python3 -m root_mcp_server.cli"],
    env=None
)

async with stdio_client(server_params) as (read, write):
    async with ClientSession(read, write) as session:
        await session.initialize()

        # Execute Python code
        result = await session.call_tool("root_python", arguments={
            "code": "import ROOT; print(ROOT.gROOT.GetVersion())"
        })
        print(result)

Available Tools

The server exposes two MCP tools:

1. root_python

Execute Python code with ROOT automatically available in scope.

Arguments:

• code (string): Python code to execute

Returns:

{
  "ok": boolean,
  "stdout": string,
  "stderr": string,
  "error": string | null,
  "error_type": string | null
}

Example:

code = """
import ROOT
h = ROOT.TH1F("h", "Gaussian", 100, -5, 5)
for i in range(10000):
    h.Fill(ROOT.gRandom.Gaus(0, 1))
print(f"Mean: {h.GetMean():.3f}")
"""

2. root_cpp

Execute C++ code via ROOT's cling interpreter.

Arguments:

• code (string): C++ code to execute

Returns:

{
  "ok": boolean,
  "stdout": string,
  "stderr": string,
  "error": string | null,
  "error_type": string | null
}

Example:

TH1F* h = new TH1F("h", "Gaussian;X;Y", 100, -5, 5);
for(int i=0; i<10000; i++) h->Fill(gRandom->Gaus(0,1));
TCanvas* c = new TCanvas("c", "Canvas", 900, 600);
h->Draw();
c->Update();
std::cout << "Mean: " << h->GetMean() << std::endl;

Features in Detail

Error Detection

The server automatically detects C++ compilation errors by:

• Checking the return code from ROOT.gInterpreter.ProcessLine()
• Scanning stderr for error keywords (error:, Error:, fatal error:)

Errors are reported with ok=false and detailed error messages.

Console Logging

All code execution is logged to stderr (MCP console) with:

• Pretty-printed code with line numbers
• Execution status (✓ success / ❌ failure)
• Complete stdout, stderr, and error details

Example output:

============================================================
EXECUTING PYTHON CODE:
  1 | import ROOT
  2 | print(ROOT.gROOT.GetVersion())
============================================================
✓ EXECUTION SUCCESS
STDOUT:
6.39/01

Graphics Support

The server initializes TApplication and supports ROOT graphics:

• TCanvas windows (batch mode can be disabled)
• Histogram plotting
• ROOT event loop for interactive graphics
• Object persistence to prevent garbage collection

Development

Running tests

# Test basic functionality
python test_mcp_client.py

# Test persistent graphics
python test_persistent_window.py

# Test histogram creation
python test_histogram.py

Project Structure

root_mcp_server/
├── root_mcp_server/
│   ├── __init__.py
│   ├── cli.py          # Entry point
│   ├── executor.py     # Code execution 
│   └── server.py       # MCP server definition
├── test_mcp_client.py
├── test_persistent_window.py
├── test_histogram.py
└── README.md

License

See LICENSE file.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Acknowledgments

• Built with the Model Context Protocol
• Powered by ROOT from CERN