xfoil-mcp - Aerodynamic polars on-call for your MCP agents

TL;DR: Wrap XFOIL in an MCP-native service so agents can request lift/drag/moment polars without touching shell scripts.

Table of contents

1. What it provides

2. Quickstart

3. Run as a service

4. Agent playbook

5. Stretch ideas

6. Accessibility & upkeep

7. Contributing

Related MCP server: Flappy MCP Server

What it provides

Quickstart

1. Install dependencies

uv pip install "git+https://github.com/Three-Little-Birds/xfoil-mcp.git"

Download XFOIL from the official MIT site and place the executable on your PATH (or point to it explicitly):

export XFOIL_BIN=/path/to/xfoil

2. Compute your first polar

from pathlib import Path
from io import StringIO

import pandas as pd

from xfoil_mcp import PolarRequest, compute_polar

airfoil_path = Path("examples/naca2412.dat")  # bundled sample airfoil
request = PolarRequest(
    airfoil_name="naca2412",
    airfoil_data=airfoil_path.read_text(encoding="utf-8"),
    alphas=[-2 + 0.5 * i for i in range(29)],  # -2 .. 12 in 0.5° steps
    reynolds=1.2e6,
    mach=0.08,
)
response = compute_polar(request)

polar_csv_path = Path("polar.csv")
polar_csv_path.write_text(response.csv, encoding="utf-8")
print("CSV stored at", polar_csv_path)

Inspect the first few rows:

df = pd.read_csv(StringIO(response.csv), comment="#")
print(df.head())

• The bundled examples/naca2412.dat follows cosine-spaced sampling (identical to XFOIL's PANE output) so you can drop it into your own scripts without re-gridding.

• The CSV header is normalised to alpha, CL, CD, CM. XFOIL may append extra columns (e.g. CDp, Cl/Cd, transition locations); those appear after the first four fields and remain untouched.

Run as a service

CLI (STDIO / Streamable HTTP)

uvx xfoil-mcp  # runs the MCP over stdio
# or python -m xfoil_mcp
python -m xfoil_mcp --transport streamable-http --host 0.0.0.0 --port 8000 --path /mcp

Use python -m xfoil_mcp --describe to view metadata and exit.

Tip (macOS/Linux): building XFOIL natively requires XQuartz/X11 headers. To avoid that setup, run the quickstart inside the repo's Docker recipe:

docker run --rm -v "$PWD/extern/xfoil-mcp:/workspace/xfoil-mcp" python:3.13-slim bash -lc '
  set -euo pipefail
  apt-get update && apt-get install -y --no-install-recommends xfoil build-essential \
    && pip install --no-cache-dir pandas /workspace/xfoil-mcp \
    && python - <<"PY"
from pathlib import Path
from io import StringIO
import pandas as pd
from xfoil_mcp import PolarRequest, compute_polar

airfoil_path = Path("examples/naca2412.dat")
request = PolarRequest(
    airfoil_name="naca2412",
    airfoil_data=airfoil_path.read_text(encoding="utf-8"),
    alphas=[-2 + 0.5 * i for i in range(29)],
    reynolds=1.2e6,
    mach=0.08,
)
response = compute_polar(request)
print(pd.read_csv(StringIO(response.csv), comment="#").head())
PY
'

Handling failures

compute_polar raises RuntimeError when XFOIL fails to emit a polar (common causes: laminar separation, too few iterations, or Reynolds numbers below ~5e4). The stderr/stdout from XFOIL is preserved in the exception message—increase ITER, seed a better initial airfoil mesh, or adjust alpha_start_deg/alpha_step_deg in response. Non-zero exit codes that still produce a polar are annotated in the CSV with a leading # xfoil exit code ... comment so you can decide whether to discard or accept the run.

FastAPI (REST)

uv run uvicorn xfoil_mcp.fastapi_app:create_app --factory --port 8001

Browse http://127.0.0.1:8001/docs to test requests and download CSVs.

python-sdk tool (STDIO / MCP)

from mcp.server.fastmcp import FastMCP
from xfoil_mcp.tool import build_tool

mcp = FastMCP("xfoil-mcp", "XFOIL polar analysis")
build_tool(mcp)

if __name__ == "__main__":
    mcp.run()

Launch:

uv run mcp dev examples/xfoil_tool.py

Connect any MCP-compatible agent (Cursor, Claude Desktop, Windsurf, ...) and ask for polars on demand.

ToolHive smoke test

Requires XFOIL_BIN pointing to the XFOIL executable:

export XFOIL_BIN=/path/to/xfoil
uvx --with 'mcp==1.20.0' python scripts/integration/run_xfoil.py
# ToolHive 2025+ defaults to Streamable HTTP; match that transport when registering
# the workload manually to avoid the legacy SSE proxy failures.

Agent playbook

• Batch sweeps - iterate through a directory of .dat files and persist each polar to object storage.

• Optimisation loops - embed the tool inside a genetic algorithm; typed responses keep mutation + evaluation deterministic.

• Visualisation - feed response.csv_path into Plotly or Matplotlib to plot Cl vs. Cd without manual parsing.

Stretch ideas

1. Compare multiple foils by merging CSVs into a parquet dataset for notebook analysis.

2. Pair with ctrltest-mcp to explore control implications from polar derivatives.

3. Schedule nightly polars via CI and publish artefacts for downstream agents.

Accessibility & upkeep

• Tests mock XFOIL so they run quickly: uv run pytest.

• Use uv run ruff check . before submitting changes.

Contributing

1. Fork and uv pip install --system -e .[dev].

2. Run the formatting and test suite.

3. Open a PR with before/after polar snippets so reviewers can verify quickly.

MIT license - see LICENSE.