UA-.NETStandard/tools/Opc.Ua.Mcp

OPC UA MCP Server

An MCP (Model Context Protocol) server that exposes OPC UA Part 4 service calls as MCP tools, enabling LLMs (Claude, Copilot, VS Code, etc.) to interact with OPC UA servers.

Features

• Profile-based tool catalog covering all OPC UA Part 4 service sets (except session management), plus PKI, configuration, NodeSet export, PubSub, and OPC UA-aware packet capture. The default full profile exposes every tool below; smaller profiles (core, services, administration, pubsub, diagnostics) expose a bounded subset — see Tool Profiles
• Both stdio and Streamable HTTP transports (HTTP is exposed only at /mcp; --transport sse is a deprecated alias for --transport http)
• JSON representation of all OPC UA types for LLM-friendly interactions; scalar Variant values preserve typed false and 0 values rather than treating default values as null
• Session management via Connect/Disconnect tools
• Embeddable — the tools ship as libraries so an application can offer OPC UA tools to an LLM alongside its own, without forking or shelling out; see Embedding

OPC UA sessions and the stateless MCP protocol

The server is built on the ModelContextProtocol 2.x SDK, which follows the 2026-07-28 specification revision and is stateless by default: there is no initialize handshake and no Mcp-Session-Id, and every request carries what it needs.

An OPC UA session is a different thing, and the distinction matters. It is a real, long-lived, secured connection to a server — application state rather than protocol state. Connect opens one and returns a name, and later tool calls pass that name back. Passing an explicit identifier is exactly the shape the stateless model asks for, so the two fit together well.

What it does assume is that the same process handles both calls. Connect on one instance and Read on another will not find the session, because the connection lives in the process that opened it. A single server process — which is what both the stdio and HTTP hosts are — is therefore the supported deployment. Running several instances behind a load balancer would need either session affinity or a shared connection broker, and neither is provided here.

Tool Inventory (full profile)

The tables below list every tool available in the default full profile. Running with --profile core|services|administration|pubsub|diagnostics|robotics|vision exposes only the tool classes relevant to that profile — see Tool Profiles for the mapping.

Service Set	Tools	Description
Connection	GetEndpoints, Connect, Disconnect, GetConnectionStatus	Endpoint discovery and session lifecycle
Attribute	Read, Write, HistoryRead, HistoryUpdate	Read/write node attributes and historical data
View	Browse, BrowseNext, TranslateBrowsePaths, RegisterNodes, UnregisterNodes, QueryFirst, QueryNext	Navigate and query the address space
Node Management	AddNodes, AddReferences, DeleteNodes, DeleteReferences	Modify address space
Method	Call	Invoke methods
Subscription	CreateSubscription, ModifySubscription, SetPublishingMode, Publish, Republish, DeleteSubscriptions, TransferSubscriptions	Notification subscriptions
MonitoredItem	CreateMonitoredItems, ModifyMonitoredItems, SetMonitoringMode, SetTriggering, DeleteMonitoredItems	Data change monitoring
Discovery	FindServers, FindServersOnNetwork, RegisterServer, RegisterServer2	Server discovery and registration
PKI Management	ListCertificates, TrustCertificate, RemoveCertificate, GetPkiStorePaths	Manage certificate trust lists
Configuration	GetConfiguration, SetTransportConfiguration, SetClientConfiguration, SetSecurityConfiguration, SetConfiguration	View/modify in-memory client settings; SetConfiguration is the full-profile compatibility tool
NodeSet Export	ExportNodeSet, ExportNodeSetPerNamespace	Export address space to NodeSet2 XML
Convenience	ReadValue, ReadValues, WriteValue, BrowseAll, CallMethod, ReadNode, Cancel	Simplified operations
Packet Capture	list_interfaces, start_capture, stop_capture, list_captures, get_capture, capture_now, list_active_channels, dump_keys, decode_pcap_with_keys, summarize_service_calls, replay_pcap, stop_replay, list_replays	OPC UA-aware packet capture, offline decode, service-call summaries, replay

Embedding the tools in your own server

The tools live in libraries, so an application that wants OPC UA tools and its own application-level tools composes them instead of running this executable:

builder.Services.AddOpcUaMcpCore();

builder.Services.AddMcpServer()
    .WithStdioServerTransport()
    .WithOpcUaMcpFilters()
    .WithOpcUaCoreTools(McpToolProfile.Services)
    .WithTools<MyApplicationTools>();

Package	Tools
OPCFoundation.NetStandard.Opc.Ua.Mcp.Core	Part 4 services, connection, configuration, PKI, NodeSet export
OPCFoundation.NetStandard.Opc.Ua.Mcp.PubSub	PubSub runtime, actions, discovery
OPCFoundation.NetStandard.Opc.Ua.Mcp.Diagnostics	UA-TCP capture, decode, replay
OPCFoundation.NetStandard.Opc.Ua.Mcp.PubSub.Diagnostics	PubSub capture, decode
OPCFoundation.NetStandard.Opc.Ua.Mcp	this ready-to-run opcua-mcp tool

See Architecture for the full picture.

Documentation

See the full documentation and NuGet readme.

Claude Desktop Configuration

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "opcua": {
      "command": "dotnet",
      "args": ["run", "--project", "/path/to/tools/Opc.Ua.Mcp/Opc.Ua.Mcp.csproj"]
    }
  }
}

VS Code Configuration

Add to .vscode/mcp.json:

{
  "servers": {
    "opcua": {
      "command": "dotnet",
      "args": ["run", "--project", "/path/to/tools/Opc.Ua.Mcp/Opc.Ua.Mcp.csproj"]
    }
  }
}

Example Tool Calls

Connect to a server

Tool: Connect
Arguments:
  endpointUrl: "opc.tcp://localhost:62541/Quickstarts/ReferenceServer"
  useSecurity: true
  autoAcceptCerts: true

Browse the Objects folder

Tool: Browse
Arguments:
  nodeId: "i=85"

Read a variable value

Tool: ReadValue
Arguments:
  nodeId: "i=2258"

Write a value

Tool: WriteValue
Arguments:
  nodeId: "ns=2;s=MyVariable"
  value: "42"
  dataType: "Int32"

Call a method

Tool: CallMethod
Arguments:
  objectId: "ns=2;s=MyObject"
  methodId: "ns=2;s=MyMethod"
  inputArguments: ["arg1", "arg2"]

OPC UA Client Configuration

The server uses McpServer.Config.xml for OPC UA client configuration, including:

• Application certificate settings
• Trust list management
• Transport quotas
• Operation limits

Certificates are stored under %LocalApplicationData%/OPC Foundation/pki/.