Proxus Industrial MCP Server

Gives AI assistants such as Claude Desktop, Cursor and VS Code read-only access to industrial devices. Supports Modbus TCP and OPC UA (Basic256Sha256, Aes128_Sha256_RsaOaep or Aes256_Sha256_RsaPss with Sign or SignAndEncrypt, or unsecured; anonymous or user-name login).

Condensed from a real session against simulated devices (docs/demo.json). More at proxus.io/tools/industrial-mcp-server.

Tools

Nothing can write to a device.

Related MCP server: OPC UA MCP Server

OPC UA security

Set security_mode (sign_and_encrypt, sign or none) and security_policy (Basic256Sha256, Aes128_Sha256_RsaOaep or Aes256_Sha256_RsaPss) per device. Certificates live in pki_dir (default pki/ next to the configuration file), in the layout most OPC UA tools use:

Trust is never automatic, in either direction:

1. On the first connection the server's certificate lands in rejected/ and the tool answers with its SHA-256 thumbprint. Confirm the thumbprint with the server's administrator, then move the file to trusted/.

2. If the server answers BadCertificateUntrusted or BadSecurityChecksFailed, it has not trusted this client yet. proxus-mcp certificate --config <file> prints this server's certificate file and thumbprint to trust on the server.

Passwords never go in the configuration file: password_env names the environment variable that holds them. Errors carry the OPC UA StatusCode name, the specification's description and a suggested next step.

Install

Download the archive for your platform from the releases page, unpack it, and point your MCP client at the proxus-mcp binary (see Claude Desktop below). Each archive has a .sha256 file next to it. The binaries are not code-signed yet: on macOS run xattr -d com.apple.quarantine proxus-mcp once after unpacking, and on Windows choose "More info, Run anyway" the first time.

proxus-mcp --version prints the version.

Docker

docker run -i --rm -v "$PWD:/config" ghcr.io/proxusiiotplatform/proxus-mcp:<version>

The image reads /config/proxus-mcp.json and speaks MCP over stdin/stdout, so an MCP client starts it with docker as the command and run -i --rm -v <folder>:/config ghcr.io/proxusiiotplatform/proxus-mcp:<version> as the arguments. Devices on the host are reachable as host.docker.internal; on Linux add --network host to reach the plant network directly. Images are published for linux/amd64 and linux/arm64.

Build

Needs the .NET 10 SDK. The protocol drivers come from the Proxus.Drivers NuGet packages (Apache-2.0).

dotnet publish src/Proxus.Mcp.Server -c Release -r osx-arm64 -o artifacts/osx-arm64

The result is one native file, artifacts/osx-arm64/proxus-mcp (about 10 MB).

Claude Desktop

Add to claude_desktop_config.json:

{
  "mcpServers": {
    "proxus": {
      "command": "/absolute/path/to/proxus-mcp",
      "args": ["--config", "/absolute/path/to/proxus-mcp.json"]
    }
  }
}

Copy proxus-mcp.example.json as a starting configuration.

Tests

• dotnet test tests/Proxus.Mcp.Tests: unit tests, no devices needed.

• tests/smoke/run_all.sh: the published binary against Modbus and OPC UA simulators (see tests/smoke/README.md).

• CI (.github/workflows/ci.yml) runs both and publishes Native AOT binaries for linux-x64, linux-arm64, win-x64 and osx-arm64.

Licence

Apache-2.0, see LICENSE.