OPC UA MCP Server

One local MCP stdio process connects one client context to one OPC UA endpoint. Use a separate process for each endpoint. Remote MCP and shared multi-client operation are gated by the identity and isolation RFC.

Features

• 🔌 Any OPC UA server — PLC, SCADA gateway or historian. Nothing to install on the plant side.
• 🧰 The whole operator toolkit — read, browse, history and aggregates, subscriptions, events and alarms, writes and method calls.
• 🛡️ Read-only by default — writes and method calls need an explicit profile, an allowlist and a pinned server certificate, and every control call is audited.
• 🐍 Python or Node — two first-class runtimes with the same tools and the same answers. Use whichever you have.
• 📦 One-file Claude Desktop install — a .mcpb bundle with nothing else to set up.

flowchart LR
    A["AI agent<br/>(Claude, Codex, Gemini, Cursor…)"] -->|MCP over stdio| B["OPC UA MCP Server<br/>(Python or Node)"]
    B -->|OPC UA| C["OPC UA server<br/>(PLC / SCADA / historian)"]

Quick start

Every MCP client runs the same command, with your endpoint in OPCUA_SERVER_URL:

npx -y opcua-mcp-server      # Node 22.13+
uvx opcua-mcp-server         # Python 3.10+

1. Add it to your agent — pick yours below.
2. Point it at a server — opc.tcp://<host>:4840, or start the bundled mock plant.
3. Ask — "What's the current temperature in the reactor vessel?"

Connect your agent

Replace opc.tcp://localhost:4840 with your endpoint. To use the Python runtime, swap npx -y opcua-mcp-server for uvx opcua-mcp-server.

npm install -g opcua-mcp-server      # or: uv tool install opcua-mcp-server
opcua-mcp-server --install claude-desktop --url opc.tcp://192.168.0.10:4840 --dry-run

claude mcp add opcua -e OPCUA_SERVER_URL=opc.tcp://localhost:4840 -- npx -y opcua-mcp-server

codex mcp add opcua --env OPCUA_SERVER_URL=opc.tcp://localhost:4840 -- npx -y opcua-mcp-server

[mcp_servers.opcua]
command = "npx"
args = ["-y", "opcua-mcp-server"]
env = { OPCUA_SERVER_URL = "opc.tcp://localhost:4840" }

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

{
  "servers": {
    "opcua": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

{
  "mcpServers": {
    "opcua": {
      "command": "npx",
      "args": ["-y", "opcua-mcp-server"],
      "env": { "OPCUA_SERVER_URL": "opc.tcp://localhost:4840" }
    }
  }
}

[!TIP] No Node or Python on the machine? Download a single-file executable from the latest release and use its path as the command — see docs/install.md. Several PLCs? Each entry talks to one endpoint, so add one entry per PLC (why).

Try it without a plant

The repo ships a simulated industrial plant — sensors, actuators, methods, history and events — so you can try every tool without touching real equipment:

git clone https://github.com/IndustriAgents/OPCUA-MCP.git && cd OPCUA-MCP
uv sync --all-packages
uv run --no-sync opcua-mock-server     # opc.tcp://localhost:4840/freeopcua/server/

Point your agent at that URL. The MCP Inspector walkthrough has prompts to try, and the compatibility matrix lists two smaller mocks for aggregates and alarms.

What you can ask

• "Show me all the variables in the system."
• "What was the temperature over the last hour? Give me the hourly average."
• "Watch the tank level and tell me what it does over the next minute."
• "What alarms are active right now?"
• "Set the valve position to 80%." — needs the operator profile
• "Start production on line 1 at 100 units/hour." — needs the operator profile

Every reading comes back with its data type, status, timestamps and engineering units — never a bare number. What a result looks like.

Tools

15 tools, identical on both runtimes and defined once in contract/tools.json. Arguments, results and limits: docs/tools.md.

Control and alarm tools also need a verified server (a secured channel and a pinned OPCUA_SERVER_CERT) unless a lab override is set. † Works only on a server that advertises the feature it needs, such as historical access.

Going to production

[!WARNING] Out of the box the agent can only read, but the OPC UA channel is unencrypted and anonymous — fine for the mock or a lab, not for real equipment. Secure the channel before connecting to anything that matters.

1. Secure the channel and pin the server — add these to the env block:

OPCUA_SECURITY_POLICY=Basic256Sha256     # implies SignAndEncrypt
OPCUA_CLIENT_CERT=/etc/opcua/client.pem  # this client's identity
OPCUA_CLIENT_KEY=/etc/opcua/client_key.pem
OPCUA_SERVER_CERT=/etc/opcua/server.pem  # pin the server you meant to reach
OPCUA_USERNAME=mcp-operator              # or OPCUA_USER_CERT for X.509
OPCUA_PASSWORD=…

2. Decide what the agent may do with OPCUA_PROFILE:

3. Keep a record — set OPCUA_AUDIT_FILE for an append-only log of every control call.

Misconfiguration stops the server at startup with a message naming the variable, rather than failing later against live equipment. The MCP policy is defence in depth, not a replacement for OPC UA authorisation: scope the OPC UA account to the same nodes and methods.

Every setting, value bounds on writes and allowlists that survive a server restart: docs/configuration.md. Threat model: SECURITY.md. Certificates: docs/certificates.md.

Documentation

Contributing

Contributions are welcome — see CONTRIBUTING.md for the project layout, local development and adding a tool to both runtimes.

The most useful thing you can send is a result from a real OPC UA server: open a compatibility report saying which server, which version and which tools worked. Test only on equipment you are authorised to use, and keep writes and method calls to a simulator or lab.

License

MIT — see LICENSE.

Tool inputs and structured results use JSON Schema draft 2020-12 with generated TypeScript/Python types and CI drift checks. See contract generation for the authoring workflow.