Codex Multisim MCP

Control NI Multisim from OpenAI Codex through a local Model Context Protocol (MCP) server. Codex can launch Multisim, place components, draw wires, save a design, and capture the Multisim window for visual verification.

The server is local and dependency-light: it uses a small Win32 bridge and a plain Node.js STDIO MCP server. No Python, AutoHotkey, npm install, cloud service, or API key is required.

Requirements

• Windows 10 or Windows 11
• NI Multisim installed locally
• OpenAI Codex app, CLI, or IDE extension
• Node.js 18 or newer

Multisim 14.0 in Simplified Chinese and English has been tested. Component dialog detection also includes a language-independent structural fallback. Other Multisim releases may need calibration through multisim_inspect_controls.

Install

1. Download codex-multisim-mcp-windows-v1.0.0.zip from GitHub Releases.
2. Extract the archive.
3. Open PowerShell in the extracted directory.
4. Run:

powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\install.ps1

The installer:

• verifies Node.js;
• copies the runtime to %LOCALAPPDATA%\MultisimMCP;
• adds a managed multisim block to ~/.codex/config.toml;
• runs an MCP protocol smoke test.

Restart Codex or open a new Codex thread after installation. Then try:

Check Multisim status, open it, and place a 74LS00 on a new design.

Project-only install

To expose the MCP only inside one trusted Codex project:

powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\install.ps1 `
  -Scope Project `
  -ProjectPath "C:\path\to\your\project"

This installs the runtime under the project's .codex\tools directory and updates that project's .codex\config.toml.

Custom Multisim location

The bridge searches the Windows file associations and standard National Instruments installation directories. If discovery fails, set:

$env:MULTISIM_EXE = "D:\NI\Circuit Design Suite\multisim.exe"

For a persistent user environment variable:

[Environment]::SetEnvironmentVariable(
  "MULTISIM_EXE",
  "D:\NI\Circuit Design Suite\multisim.exe",
  "User"
)

Restart Codex after changing the persistent variable.

Available tools

Tool	Purpose
multisim_status	Detect Multisim and report its active window
multisim_launch	Start Multisim or open a design
multisim_new_design	Create a blank design
multisim_place_component	Search and place a database component
multisim_wire	Draw a wire through optional explicit via points
multisim_auto_route	Draw a one-bend Manhattan route
multisim_save_design	Save or Save As
multisim_screenshot	Capture the Multisim window
multisim_inspect_controls	Inspect controls for version calibration

Coordinate model

Placement and wiring coordinates are physical pixels relative to the top-left corner of the Multisim main window. A reliable Codex workflow is:

1. call multisim_status;
2. call multisim_screenshot;
3. place components;
4. capture another screenshot;
5. wire the visible pin endpoints;
6. verify and save.

multisim_auto_route is deterministic one-bend routing, not a full PCB or schematic obstacle-solving router. Use explicit via points with multisim_wire for multi-bend routes.

Uninstall

powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\uninstall.ps1

For a project-only installation:

powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\uninstall.ps1 `
  -Scope Project `
  -ProjectPath "C:\path\to\your\project"

The uninstaller removes only the marked configuration block managed by this project. Other Codex settings and MCP servers are left untouched.

Build from source

The release archive and repository include bin\multisim-cli.exe. To rebuild it using the .NET Framework compiler included with Windows:

powershell.exe -NoProfile -ExecutionPolicy Bypass -File .\build.ps1
node .\test\protocol-smoke.js

Create a GitHub-ready release archive:

powershell.exe -NoProfile -ExecutionPolicy Bypass `
  -File .\scripts\package-release.ps1

Security notes

This MCP controls a desktop application with simulated keyboard and mouse input. Codex is configured to prompt before state-changing Multisim tools. Review requested actions before approval, especially Save As paths.

License

MIT