Modbus MCP Server

An MCP server that standardizes and contextualizes Modbus data, enabling seamless integration of AI agents with industrial IoT systems.

Features

• Modbus Tools:

  • Read/write holding registers (read_register, write_register).

  • Read/write coils (read_coils, write_coil).

  • Read input registers (read_input_registers).

  • Read multiple holding registers (read_multiple_holding_registers).

• Prompt: Analyze Modbus register values with a customizable prompt (analyze_register).

• Flexible Connections: Supports Modbus over TCP, UDP, or serial, configured via environment variables.

Requirements

• Python: 3.10

• uv for dependency and virtual environment management.

Installation

1. Install :

   curl -LsSf https://astral.sh/uv/install.sh | sh

2. Clone the Repository:

   git clone https://github.com/kukapay/modbus-mcp.git cd modbus-mcp

3. Install Dependencies:

   uv sync

Configuration

The server connects to a Modbus device using parameters specified via environment variables. Set these variables in a .env file or your shell environment.

Environment Variables

Example .env File

For TCP:

For Serial:

Usage

Installing for Claude Desktop

The configuration file:

Using Tools

Note: Natural language support depends on the client’s ability to parse and map prompts to tools. The MCP Inspector requires structured JSON, but the examples below show how conversational inputs translate.

1. Read a Holding Register:

   • Prompt:

     Please read the value of Modbus holding register 0.

   • MCP Inspector JSON:

     { "tool": "read_register", "parameters": {"address": 0, "slave_id": 1} }

   • Expected Output: Value: <register_value>

2. Write to a Holding Register:

   • Prompt:

     Set Modbus holding register 10 to the value 100.

   • MCP Inspector JSON:

     { "tool": "write_register", "parameters": {"address": 10, "value": 100, "slave_id": 1} }

   • Expected Output: Successfully wrote 100 to register 10

3. Read Coils:

   • Prompt:

     Check the status of the first 5 Modbus coils starting at address 0.

   • MCP Inspector JSON:

     { "tool": "read_coils", "parameters": {"address": 0, "count": 5, "slave_id": 1} }

   • Expected Output: Coils 0 to 4: [False, False, False, False, False]

4. Write to a Coil:

   • Prompt:

     Turn on Modbus coil 5.

   • MCP Inspector JSON:

     { "tool": "write_coil", "parameters": {"address": 5, "value": true, "slave_id": 1} }

   • Expected Output: Successfully wrote True to coil 5

5. Read Input Registers:

   • Prompt:

     Read the values of 3 Modbus input registers starting from address 2.

   • MCP Inspector JSON:

     { "tool": "read_input_registers", "parameters": {"address": 2, "count": 3, "slave_id": 1} }

   • Expected Output: Input Registers 2 to 4: [<value1>, <value2>, <value3>]

6. Read Multiple Holding Registers:

   • Prompt:

     Get the values of Modbus holding registers 0 through 2.

   • MCP Inspector JSON:

     { "tool": "read_multiple_holding_registers", "parameters": {"address": 0, "count": 3, "slave_id": 1} }

   • Expected Output: Holding Registers 0 to 2: [<value1>, <value2>, <value3>]

License

This project is licensed under the MIT License. See LICENSE for details.