SimConnect MCP Server

An MCP (Model Context Protocol) server that connects AI coding agents to Microsoft Flight Simulator via SimConnect. This server is built for add-on development — full read/write access to SimVars, L-vars, events, calculator code execution, and embedded documentation.

What It Does

• Read/write any SimVar — altitude, heading, speed, autopilot settings, engine parameters, and 1,080+ more from a comprehensive built-in catalog, with unit selection and honest failures on a rejected write
• Read/write L-vars — aircraft-specific local variables used by add-on developers (Fenix A320, FlyByWire A32NX, PMDG, etc.), including live enumeration of what the loaded aircraft has actually registered
• PMDG 777 and 737 NG3 native SDK support — direct access to all aircraft data fields and control events via the PMDG SDK Client Data Areas, plus CDU screen reading with colors/formatting
• Trigger events — toggle switches, set autopilot modes, control lights, fire custom MobiFlight events
• Execute RPN calculator code — run arbitrary Reverse Polish Notation code directly in the sim
• Search and discover variables — searchable catalogs of SimVars, events, and aircraft-specific L-vars with human-readable names and valid values
• Facilities lookup — nearby airports sorted by distance and detail lookup for a specific airport, waypoint, NDB or VOR by ICAO identifier, read directly from SimConnect's facility subscription
• Flight and scenario tools — load and save .FLT flights, load a .PLN flight plan, and spawn an AI aircraft or object, for scripting test scenarios instead of setting them up by hand
• Embedded documentation — SimConnect reference docs served as MCP resources, available offline
• Aircraft-specific catalogs — pre-built variable databases with panel groupings, display names, and value descriptions. Ships with 1,607 PMDG 777 variables (777-200LR/200F/300ER/F) and 1,861 PMDG 737 NG3 variables (-600/700/800/900 incl. BBJ/BDSF/BCF).
• HubHop integration — search the MobiFlight HubHop community preset database directly as an MCP tool, or use the built-in client to generate and extend L-var catalogs for any supported aircraft

Prerequisites

• Microsoft Flight Simulator (MSFS 2020 or 2024) running on the same machine
• uv — provides uvx, which fetches the server and its Python runtime for you
• MobiFlight WASM Module (optional, for L-var support) — install in your MSFS Community folder. Download from MobiFlight

Installation

Published on PyPI as simconnect-mcp, and listed in the MCP Registry as io.github.robin24/simconnect-mcp.

Once uv is installed, no separate install step is needed — uvx fetches and runs the server on demand:

uvx simconnect-mcp

That starts the server on stdio, which is what an MCP client does for you. Run it by hand only to check that it starts; press Ctrl+C to stop.

To pin a version, use uvx simconnect-mcp@1.0.1.

From source (for development)

git clone https://github.com/robin24/simconnect-mcp.git
cd simconnect-mcp

# Creates the virtual environment and installs the dev group too
uv sync

Configuring as an MCP Server

Claude Code

Via CLI:

claude mcp add --transport stdio simconnect -- uvx simconnect-mcp

Or to make it available across all projects:

claude mcp add --transport stdio --scope user simconnect -- uvx simconnect-mcp

Via JSON (~/.claude/settings.json or project-level .claude/settings.json):

{
  "mcpServers": {
    "simconnect": {
      "command": "uvx",
      "args": ["simconnect-mcp"]
    }
  }
}

OpenAI Codex CLI

Via CLI:

codex mcp add simconnect -- uvx simconnect-mcp

Via JSON:

{
  "mcpServers": {
    "simconnect": {
      "command": "uvx",
      "args": ["simconnect-mcp"]
    }
  }
}

Gemini CLI

Via CLI:

gemini mcp add --transport stdio simconnect -- uvx simconnect-mcp

Via JSON (~/.gemini/settings.json):

{
  "mcpServers": {
    "simconnect": {
      "command": "uvx",
      "args": ["simconnect-mcp"]
    }
  }
}

MCP Inspector (Interactive Testing)

uv run mcp dev src/simconnect_mcp/server.py

Note: To run a local checkout instead of the published package, replace uvx simconnect-mcp with uv run --directory /path/to/simconnect-mcp simconnect-mcp, using the absolute path to your clone.

Tools (32)

Every tool is prefixed msfs_, carries explicit readOnlyHint/destructiveHint annotations, and returns a typed result or a structured error — never a fabricated success. The tables below are generated from the live server (name, kind, and title come straight from each tool's ToolAnnotations); descriptions are the one-line summary from the tool's own docstring:

uv run python -c "
import asyncio
from simconnect_mcp.server import mcp
async def m():
    for t in sorted(await mcp.list_tools(), key=lambda x: x.name):
        kind = 'read' if t.annotations.readOnlyHint else 'write'
        print(f'| \`{t.name}\` | {kind} | {t.annotations.title} |')
asyncio.run(m())"

Connection (3)

SimVar Operations (6)

Units: msfs_get_simvar (and msfs_set_simvar) accept an optional unit argument and always report the unit actually used in the result. Omit unit and the bundled SimVar catalog supplies a sensible default for that variable; for a variable the catalog doesn't know, the default is "number".

Event Operations (3)

L-Var Operations (6)

msfs_list_lvars asks the MobiFlight WASM module to enumerate what the aircraft has actually registered, live — but the module caps its reply at 1000 names and still reports the list as complete when it truncates. A busy add-on setup (GSX and similar) can crowd the aircraft's own variables out of the response entirely; watch for truncated: true. Treat the catalogs and the live listing as a starting point, not a guaranteed inventory — msfs_get_lvar reads any name you supply, whether or not it surfaced in either one.

Aircraft State (1)

Facilities (2)

Airports are world-wide (SimConnect returns the full 85,249-airport list, cached after the first collection). Waypoints, NDBs and VORs are scoped to wherever the aircraft currently is, so they are re-collected on every call rather than cached — a cached navaid list would keep answering for the aircraft's previous position after a reposition or a flight.

Utilities (2)

PMDG 777 / 737 NG3 (3)