ThinkPLC-MCP

ThinkPLC-MCP is a server designed to interface with SIEMENS PLC S7-1500/1200 using their JSON-RPC 2.0 API. It exposes API functionalities as MCP tools, enabling AI assistants and other MCP-compatible clients to interact with the PLC programmatically.

🔧 Features

• Connects to a SIEMENS PLC API (Webserver) endpoint

• Provides MCP tools for:

  • ✅ User authentication (login, logout, ChangePassword-user)

  • ✅ Check PLC connectivity (ping)

  • ✅ Retrieve user permissions via Api-GetPermissions after login

  • ✅ Get API version with Api-Version

  • ✅ List available API methods using Api-Browse

  • ✅ Retrieve structure information with Api-GetQuantityStructures

  • ✅ Get password security policies with Api-GetPasswordPolicy

  • ✅ Browse tags and metadata using PlcProgram-Browse

  • ✅ Read single variables via PlcProgram-Read

  • ✅ Write Boolean, Number, or String tags with PlcProgram-Write-*

  • ✅ Read the current CPU operating mode with Plc-ReadOperatingMode

  • ✅ Request a change of operating mode using Plc-RequestChangeOperatingMode

  • ✅ Read the CPU system time (Plc-ReadSystemTime)

  • ✅ Set the CPU system time (Plc-SetSystemTime)

  • ✅ Read available project languages (Project-ReadLanguages)

  • ✅ Browse active alarms (Alarms-Browse)

  • ✅ Acknowledge alarms (Alarms-Acknowledge)

  • ✅ Browse diagnostic buffer entries (DiagnosticBuffer-Browse)

• 🔄 Optional: automatic service account login with token refresh

Related MCP server: OPC UA MCP Server

⚙️ Prerequisites

• Node.js (v18.x or later recommended)

• npm (comes bundled with Node.js)

• Access to a running SIEMENS PLC API (Webserver)

⚙️ Configuration

This server uses a config.js file written in ES Module syntax.

Example config.js:

export const config = {
  URL: "https://<PLC-IP-Address>/api/jsonrpc", // required
  userName: "your-username", // optional
  pwr: "your-password", // optional
};

🚀 Getting Started

1. Navigate to the project folder:

cd your-project-directory

2. Install dependencies:

npm install

3. Edit config.js as shown above.

4. Start the server

node start

🖥️ Connecting with Claude Desktop

To use this MCP server with Claude AI (desktop version):

1. Find or create the claude_desktop_config.json file (typically in the Claude app config folder).

2. Add or update the following:

{
  "mcpServers": {
    "ThinkPLC-MCP": {
      "command": "npx",
      "args": ["mcp-remote", "http://localhost:5000/mcp"]
    }
  }
}

4. Ensure @modelcontextprotocol/tools is installed:

npm install -g @modelcontextprotocol/tools