Connect an AI assistant to TIA Portal through MCP (Claude Desktop, Claude Code and other clients)

An AI assistant can read and edit a TIA Portal V21 project through MCP. The tia MCP server is a small npm package that talks to PLCWare's serve app, the Windows program that does the Openness work. The assistant prepares the work; a person approves anything that reaches a real PLC. This guide connects the two. It applies to TIA Portal V21.

[ your AI client ]  --(MCP/stdio)-->  [ tia MCP (npx) ]  --(HTTP)-->  [ serve (Windows + TIA Portal V21) ]

What you need

• A Windows machine with TIA Portal V21 and the PLCWare app (serve) running with an activated license. In the tray app, License tab: paste your key and save; API tab: Start API (default port 5000). From a command line: TIAOpenness.exe serve 5000.
• Node.js (version 20 or later) on the machine that runs your AI client. The MCP runs through npx, so there is nothing else to install.
• One setting, TIA_API_BASE, the address of serve. The MCP sends no key: what activates the app is the license on the host.

Claude Code

One command, at user scope (it applies to all your projects):

claude mcp add tia --scope user -e TIA_API_BASE=http://localhost:5000 -- npx -y @renanlido/tia-openness-mcp

Put the server name (tia) first. -e takes several values, and Claude Code 2.1.238 rejected --env KEY=VALUE written before the name. Check with claude mcp list, which should show tia as connected, and with /mcp inside a session.

Claude Desktop

Edit claude_desktop_config.json. In Claude Desktop, Settings > Developer > Edit Config opens it:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "tia": {
      "command": "npx",
      "args": ["-y", "@renanlido/tia-openness-mcp"],
      "env": { "TIA_API_BASE": "http://localhost:5000" }
    }
  }
}

Restart the app. On Windows, start with plain npx as above. If the client reports that the server failed to start, use the cmd /c form, which exists only on Windows:

"command": "cmd", "args": ["/c", "npx", "-y", "@renanlido/tia-openness-mcp"]

Keep a single tia entry: two servers would both talk to the same serve, which runs one operation at a time.

Other clients

Codex, Gemini CLI, Cursor, VS Code and Windsurf use the same command, npx -y @renanlido/tia-openness-mcp, and the same TIA_API_BASE variable; only the place where each client keeps its configuration differs. The exact format for each is in the Installation manual.

When your AI client is on another machine

A common setup is an editor on a Mac and serve in a Windows VM. On the Windows side, allow remote access in the tray app (API tab, Allow remote access..., which reserves the URL and opens the firewall port), set the host to 0.0.0.0 and start the API; from a command line, TIAOpenness.exe serve 5000 --host 0.0.0.0. The license must be activated on that machine. On the client side, put the VM's address in the MCP entry itself, in place of http://localhost:5000. The entry's TIA_API_BASE is what the MCP reads: a variable exported in your shell does not replace it.

For Claude Code, add the server again with the VM's address (if tia is already registered, remove it first with claude mcp remove tia):

claude mcp add tia --scope user -e TIA_API_BASE=http://<vm-ip>:5000 -- npx -y @renanlido/tia-openness-mcp

For Claude Desktop and the other clients that keep a JSON configuration, change the value in the file:

"env": { "TIA_API_BASE": "http://<vm-ip>:5000" }

Then start a new session, or restart the app, so that the MCP starts with the new address.

The license activates the server; it does not identify who calls it. Control access with a firewall or VPN.

Check the connection

Ask the assistant to call tia_ping. It answers { base, reachable, activated, latencyMs, hint }:

• reachable: false: the address, the port or the firewall is wrong, or serve is not running.
• activated: false: the license on the host is missing or invalid.
• Both true: serve is reachable and activated. That is not the same as ready: call tia_readiness to check the Windows group, x64 and the TIA Portal installation (Set up TIA Portal Openness on Windows).

Then tia_status and tia_connect open or attach to a project. The first connection of a serve process can raise a security prompt in TIA Portal on the Windows machine, and only a person can answer it.

What to ask

• "List the blocks of PLC_1 and tell me which ones are not consistent." (tia_plc_blocks)
• "Export FB_Motor and check that it matches the file in git." (tia_export_block, tia_block_compare)
• "Write an SCL function block that does X, put it in the project and compile." (tia_source_put, tia_compile)
• "Compile PLC_1 and summarize the errors." (tia_compile)

The tools are grouped by what they can change: reads (class R) change nothing; offline changes (class M-off) edit the project but never touch a PLC; a few gated tools reach the physical world.

What the assistant cannot do alone

• Download to a PLC. tia_download first returns a plan and a single-use planHash for a person to review; only after the person approves does it run again with approved: true and the same planHash. If the software changed in between, serve refuses with 409 plan_stale. The assistant never approves.
• Go online, upload a station, scan the network. Each is a gate that needs a person.
• Secrets. A master secret, a know-how password, a certificate password or the password policy always come from a person. The assistant never invents one.
• Safety (F) logic. Never authored, changed or downloaded autonomously.
• Two things at once. serve has one serial worker. Long operations (connect, compile, download...) may answer status: "running" with a jobId; the assistant then waits with tia_job_status instead of repeating the call.

Read-only mode

To try the MCP with no write risk, set TIA_MCP_MODE to read-only in the server's env:

"env": { "TIA_API_BASE": "http://localhost:5000", "TIA_MCP_MODE": "read-only" }

The MCP then registers only the read tools: no tool that changes the project or touches a controller is even listed. Because tia_start and tia_connect are not read tools, the assistant cannot open a project in this mode: the project must already be open in serve.

This guards against the assistant, not against a person: it lives in the MCP, and the license scopes on serve stay the authority. An MCP release that predates the mode ignores the variable and registers every tool, so check npx -y @renanlido/tia-openness-mcp --version (the flag exists from 1.9.2) and confirm in your client that a write tool such as tia_compile is missing.

Which plan does what

Basic reads the project, authors offline (blocks, tags, hardware) and compiles. Pro adds downloading to a real PLC and going online, always behind the human gates above. The 30-day trial includes the Pro scopes.

For a guided flow from a specification to a verified project, the open-source tia-harness plugin for Claude Code adds skills and subagents on top of the same MCP.

Related guides

• Set up TIA Portal Openness on Windows
• Compile a PLC from code and read the messages
• Installation manual
• All guides

Start your free 30-day trial

PLCWare runs these steps for you, or for your AI assistant, against TIA Portal V21. The trial lasts 30 days, includes the Pro scopes, needs no card and does not renew. You need TIA Portal V21 with a STEP 7 Professional license, bought separately from Siemens.

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