MCP Arduino Server (mcp-arduino-server)

MCP Server for Arduino CLI providing sketch, board, library, and file management tools. Powered by FastMCP.

Quick Start

Install from PyPI and run:

pip install mcp-arduino-server
mcp-arduino-server

Overview

This server acts as a bridge between the Model Context Protocol (MCP) and the arduino-cli, allowing AI agents or other MCP clients to interact with Arduino development workflows. It provides tools for managing sketches, compiling code, uploading to boards, managing libraries, discovering hardware, and performing basic file operations within a restricted environment.

Features

• Sketch Management: Create, list, read, and write Arduino sketches (.ino, .h files).

  • Writing the main .ino file automatically triggers compilation for validation.
  • Auto-Open: Newly created .ino files are automatically opened in your default editor.

• WireViz Circuit Diagrams:

  • YAML Authoring Help: Use the built-in getWirevizInstructions tool to fetch comprehensive guidelines and an example for creating valid WireViz YAML. The instructions cover how to define connectors (components), cables, connections, and required metadata, along with a checklist and color code reference.

  • Diagram Generation: Use the generate_diagram_from_yaml tool to generate a circuit diagram PNG from your YAML. You can specify a sketch directory for output, or let the tool create a timestamped folder. The PNG is returned as base64 and opened automatically in your image viewer.

  • Typical Workflow:

    1. Call getWirevizInstructions to see the YAML structure and example.
    2. Author your YAML to describe your Arduino circuit.
    3. Call generate_diagram_from_yaml with your YAML to get a ready-to-use PNG wiring diagram.

  • Error Handling: The server validates YAML structure, manages output files, and provides clear error messages for invalid YAML, missing dependencies, or WireViz failures.

  • Example YAML: (see the output of getWirevizInstructions for a full template)

    connectors:
      Arduino Uno:
        pinlabels: ["5V", "GND", "D2", "D3", "A4", "A5"]
        notes: Main control board
      SSD1306 OLED Display:
        pinlabels: ["VCC", "GND", "SCL", "SDA"]
        notes: Display module
      # ... more components ...
    cables:
      W_SSD1306_OLED:
        colors: [RD, BK, TQ, VT]
        category: bundle
    connections:
      - # Example connection
        - Arduino Uno: [3]
        - W_SSD1306_OLED: [1]
        - SSD1306 OLED Display: [1]
    metadata:
      description: "Wiring diagram for Arduino Uno with SSD1306 OLED Display and Push Buttons"
      author: "User"
      date: "2024-06-23"
    

• Code Verification: Compile sketches using verify_code without uploading.

• Uploading: Compile and upload sketches to connected boards.

• Library Management:

  • Search the online Arduino Library Manager index.
  • Search local platform libraries (fuzzy search if thefuzz is installed).
  • Install libraries from the index.
  • List examples from installed libraries.

• Board Management:

  • Discover connected boards and their details (Port, Name, FQBN).
  • List platform libraries associated with connected boards.
  • Search the online board index for FQBNs.

• File Operations: Basic, restricted file reading, writing, renaming, and removal within the user's home directory or designated sketch directories.

  • Security: Operations are sandboxed primarily to ~/Documents/Arduino_MCP_Sketches/ and the user's home directory (~) with strong warnings for destructive actions.

• Robust Error Handling & Logging: Extensive logging, improved error messages, and strict path validation for all file operations. Security is emphasized throughout.

Prerequisites

• Python: 3.8+ (3.10+ recommended; required by dependencies like mcp[cli])
• arduino-cli: Must be installed and accessible in the system PATH or common locations (e.g., /usr/local/bin, /opt/homebrew/bin). The server attempts auto-detection.
• WireViz: Required for circuit diagram generation. Install and ensure it's in your PATH.
• MCP SDK: Installed via the project dependencies (mcp[cli]).
• Fuzzy Search (Optional but Recommended): Installed via project dependencies (thefuzz[speedup]>=0.20.0). Enables fuzzy matching for local library search.

Installation

Install via pip (recommended for most users):

pip install mcp-arduino-server

For development or advanced usage, clone the repository and install dependencies:

git clone https://github.com/Volt23/mcp-arduino-server.git
cd mcp-arduino-server
pip install .

Set up Python 3.10+: Ensure you have Python 3.10 or newer. Using pyenv is recommended:

pyenv install 3.11.6 # Or latest 3.10+
pyenv local 3.11.6

Ensure arduino-cli is installed and configured:

• Follow the official arduino-cli installation guide.
• You may need to install board cores (e.g., arduino-cli core install arduino:avr).

Configuration

The server uses the following default paths and settings. Some can be overridden via environment variables.

• Sketches Base Directory: ~/Documents/Arduino_MCP_Sketches/
• Build Temp Directory: ~/Documents/Arduino_MCP_Sketches/_build_temp/
• Arduino Data Directory: Auto-detected (~/.arduino15 or ~/Library/Arduino15)
• Arduino User Directory: ~/Documents/Arduino/
• Arduino CLI Path: Auto-detected via shutil.which and common paths. Override with ARDUINO_CLI_PATH environment variable.
• WireViz Path: Auto-detected via shutil.which (expects wireviz command). Override with WIREVIZ_PATH environment variable.
• Default FQBN (for auto-compile on write): arduino:avr:uno. Override via the board_fqbn argument in write_file.
• Log Level: Controlled by the LOG_LEVEL environment variable (e.g., DEBUG, INFO, WARNING). Defaults to INFO.

Usage

Run the server using the installed command-line script within its environment:

• Using uv:

  uv run mcp-arduino-server
  

• Using pip (with activated venv):

  # Ensure your virtual environment is activated (source .venv/bin/activate)
  mcp-arduino-server
  

Using WireViz Tools

• YAML Authoring Help: Call getWirevizInstructions() to receive comprehensive guidelines, a checklist, and a ready-to-use example for authoring valid WireViz YAML for Arduino diagrams.
• Diagram Generation: Call generate_diagram_from_yaml(yaml_content: str, sketch_name: str = "", output_filename_base: str = "circuit") to generate a PNG wiring diagram from your YAML. The tool validates your YAML, manages output files, returns a confirmation and the PNG image (base64), and opens it automatically in your image viewer.
• Workflow:
  1. Use getWirevizInstructions to learn the YAML format.
  2. Write your YAML describing your circuit.
  3. Use generate_diagram_from_yaml to create and view your diagram.

Auto-Open Feature

• When you create a new sketch or generate a diagram, the relevant file will open automatically in your system's default application (editor or image viewer).

Error Handling

• All file operations and CLI interactions include robust error messages and logging. Check logs for troubleshooting details.

The server will start and listen for connections from an MCP client via standard input/output (stdio).

Integrating with MCP Clients (e.g., Claude Desktop)

When configuring an MCP client (such as Claude Desktop) to launch this server, you must ensure the command in your JSON config points to the correct executable. If you are using pyenv or a custom Python environment, specify the full path to the mcp-arduino-server binary where it was installed.

For example, to ensure WireViz is always found regardless of PATH issues, you can set the WIREVIZ_PATH environment variable in your MCP client config if supported:

{
  "mcpServers": {
    "arduino": {
      "command": "/Users/<your-username>/.pyenv/versions/<your-python-version>/bin/mcp-arduino-server",
      "args": [],
      "env": {
        "WIREVIZ_PATH": "/Users/<your-username>/.pyenv/versions/<your-python-version>/bin/wireviz"
      }
    }
  }
}

Replace <your-username> and <your-python-version> with your actual username and Python version. This ensures the MCP client launches the correct environment and always finds WireViz, even if your PATH is not set up for GUI apps.

Replace <your-username> and <your-python-version> with your actual username and Python version as appropriate. This ensures the MCP client launches the correct environment and finds all dependencies.

Available Tools (MCP Interface)

The following tools are exposed via the MCP interface:

• create_new_sketch(sketch_name: str): Creates a new sketch directory and .ino file.
• list_sketches(): Lists valid sketches in the sketches directory.
• read_file(filepath: str): Reads a file; concatenates all .ino/.h files if reading the main sketch .ino.
• write_file(filepath: str, content: str, board_fqbn: str = DEFAULT_FQBN): Writes content to a file; restricted paths; auto-compiles main .ino files.
• rename_file(old_path: str, new_path: str): Renames/moves a file/directory within the home directory.
• remove_file(filepath: str): Removes a file (not directories) within the home directory. Irreversible.
• list_boards(): Lists connected boards, their FQBNs, and platform libraries.
• board_search(board_name_query: str): Searches the online index for board FQBNs.
• verify_code(sketch_name: str, board_fqbn: str): Compiles a sketch without uploading.
• upload_sketch(sketch_name: str, port: str, board_fqbn: str): Compiles and uploads a sketch.
• lib_search(library_name: str, limit: int = 15): Searches online and local platform libraries.
• lib_install(library_name: str): Installs/updates a library from the index.
• list_library_examples(library_name: str): Lists examples for an installed library.
• getWirevizInstructions(): Returns detailed YAML authoring instructions and a template for WireViz diagrams.
• generate_diagram_from_yaml(yaml_content: str, sketch_name: str = "", output_filename_base: str = "circuit"): Generates a PNG wiring diagram from YAML, returns image and confirmation, opens PNG automatically.

Refer to the server script's docstrings (src/mcp_arduino_server/server.py) for detailed arguments, return values, and potential errors for each tool.

Debugging Tips

• Check Server Logs: Detailed errors from arduino-cli are logged by the server. Increase verbosity with export LOG_LEVEL=DEBUG.
• Permissions: Ensure the user running the server has write access to sketch/build directories and read/write access to serial ports (e.g., add user to dialout group on Linux).
• Environment PATH: Verify arduino-cli and necessary toolchains (e.g., avr-gcc, bossac) are in the PATH accessible to the server process.
• Cores/Toolchains: Use arduino-cli core install <core_spec> (e.g., arduino:avr) if compilation fails due to missing cores.
• arduino-cli Commands: Test arduino-cli commands directly in your terminal to isolate issues.

License

This project is licensed under the MIT License.