Connect your AI assistant

Ask Claude, ChatGPT or Grok for airfoil and wing work in plain language — they run the real tools.

You are not charged for the conversation; your AI subscription pays for that. foil.tools charges credits only for optimization and 3D wing analysis. Searching, geometry, stored polars and 2D analysis are free.

Before you start

A free foil.tools account — it holds the quota, credits and saved designs the connector uses.
Nothing else for Claude, ChatGPT or Grok — you paste one URL and sign in. No API key.
Credits only for optimization and wing analysis — each account gets a free monthly allowance first.

Connecting grants the assistant access to your whole foil.tools account: it can spend credits on optimization and wing analysis, save airfoils and wing designs into your account, and read back everything already saved there. It cannot delete or overwrite anything. There is no read-only connection and no spending ceiling — disconnect it if that is not what you want.

Claude

Works on claude.ai, the desktop app and mobile — the connector follows your account.

1
Open Settings (your name, bottom-left) → Connectors. It sits under the Customize heading, not Settings.
2
Top right, click Add → Add custom connector. It is a dropdown rather than a button, which is easy to miss.
3
Paste as the URL and click Add.
4
Click Connect, sign in to foil.tools, and approve. The tools appear in your chats.

Claude Code, from a terminal — same sign-in, no key:

claude mcp add --transport http foiltools https://foil.tools/api/mcp

Then try: “Using foil.tools, find me a section for a hydrofoil at Re 500,000 and CL 0.6, and show me its drag polar.”

ChatGPT

Custom connectors live behind Developer mode, which is web-only and needs a Plus, Pro, Business, Enterprise or Edu plan. On Business and Enterprise an admin may have to allow custom connectors first.

1
Settings → Apps → Advanced settings → turn on Developer mode.
2
Settings → Connectors → Create.
3
Name it foil.tools, paste , and use this description verbatim — ChatGPT reads it to decide whether the connector is relevant:Airfoil and wing design tools. Search a library of thousands of airfoils, retrieve real lift and drag polars, run NeuralFoil 2D analysis, optimize airfoil sections, and analyze 3D wings.
4
Set Authentication to OAuth, click Create, then Connect and sign in to foil.tools.

Without Developer mode, foil.tools still appears in Deep Research and company-knowledge searches, where it can search the library and read airfoil records but cannot run analyses. That is the mode working as designed, not a broken connector.

Grok

1
Go to grok.com/connectors. On Business and Enterprise, an admin provisions the connector first.
2
New Connector → Custom.
3
Paste and sign in. Grok discovers the tools itself.

Any other MCP client

Cursor, Zed, your own scripts and other agent frameworks use an API key instead of signing in. Generate one at Dashboard → API Keys (up to 5 per account).

{
  "mcpServers": {
    "foiltools": {
      "type": "http",
      "url": "https://foil.tools/api/mcp",
      "headers": { "Authorization": "Bearer ft_YOUR_KEY" }
    }
  }
}

An API key spends your account’s credits and never expires until you revoke it. Treat it like a password, and prefer a connector where you have the choice.

Managing access

Disconnect a connector in your assistant’s own settings — Claude, ChatGPT and Grok each list it under Connectors.
API keys are separate and are revoked at Dashboard → API Keys.
Revoking never touches your saved foils, wing designs or credits.

What your assistant can do

The six read tools are new. Your assistant only sees them after you disconnect and reconnect the connector — see Troubleshooting for why.

Tool	What it does	Cost
search_airfoils	Search thousands of airfoils by name, family, thickness or camber	Free
get_airfoil	Geometry, thickness, camber, CST parameters, coordinates	Free
get_polar	Stored NeuralFoil lift/drag/moment curves	Free
search_by_operating_point	Rank airfoils by drag at a target CL and Reynolds number	Free
find_airfoil	Weighted multi-point selector — scored on drag, Clmax, stall gentleness, pitching moment, efficiency and L/D placement; a point can be marked a constraint (checked, not scored) for a stall or load requirement	Free
analyze_airfoil	NeuralFoil 2D analysis, optional trailing-edge flap	Free · 120/hr
optimize_airfoil	Inverse design — optimizes a section for your operating points	3 credits
analyze_wing	3D wing analysis (AeroBuildup or VLM), and where the wing stalls first	1–3 credits
analyze_trim	Trim an aircraft — a wing plus a stabiliser about a CG, on LiftingLine: trim angle, stabiliser setting, per-surface loads, static margin, required thrust. Paid-only, unlimited on Pro. New: reconnect to see it	2 credits a point · 3 a sweep
search / fetch	Library research pair, required by ChatGPT connectors	Free
save_airfoil	Save a section to your account — Dashboard → Foils	Free
save_wing_design	Save a wing so it reopens in the designer — Dashboard → Wings	Free
save_wing_analysis	Save an analysis run — Dashboard → Wing Analyses	Free
list_saved_airfoils	What is already in your account — names and dates, not geometry	Free
get_saved_airfoil	One saved section back, with its CST parameters	Free
list_wing_designs	Your saved wings, with their planform parameters	Free
get_wing_design	One saved wing back in full, splines included	Free
list_wing_analyses	Your saved runs, optionally filtered to one design	Free
get_wing_analysis	One saved run back in full — no credits to re-read	Free

Requests are capped at 600/hour per key. Free monthly allowances apply before credits are touched — ask your assistant how many credits you have, or check the dashboard. VLM wing analysis can take several minutes; that is the solver working, not a hang.

Troubleshooting

“Failed to connect” or “Could not reach server”: Check the URL is exactly — no trailing slash, no /sse.
401 / “Authorization required”: In a connector, disconnect and reconnect to sign in again. In a script, the API key goes in an Authorization: Bearer ft_… header.
Sign-in opens but ends on an error: You are probably signed into a different foil.tools account in that browser. Sign out at foil.tools, then reconnect.
The assistant never uses the tools: Name it once: “Using foil.tools, …”. In ChatGPT, check the connector Description matches the wording above — the model reads it to decide relevance.
ChatGPT only searches and never analyses: Developer mode is off, or you are in Deep Research. Both limit a connector to search and fetch.
“Monthly quota exceeded”: The free allowance for optimization or wing analysis is used up. Buy credits, or wait for the reset on the 1st.
“Analysis rate limit reached”: 2D analysis is free but capped at 120/hour. Batch several Reynolds numbers into one call with re_values instead of looping.
A tool you were told about is missing: Your client cached the tool list when it connected. This server is stateless, so it cannot push a tools/list_changed notification — disconnect the connector and reconnect to pick up tools added since.
“Storage limit reached” when saving: A free account holds 10 saved airfoils, 10 wing designs and 10 analyses. Delete something in the dashboard and retry.
A wing analysis times out: VLM at high panel counts is slow. Ask for AeroBuildup, or fewer spanwise panels.
It quotes a sweep angle that looks wrong: Ask it to report quarter-chord sweep explicitly — the wing designer’s sweep control is not the quarter-chord angle.

Still stuck? Get in touch.

Privacy and safety

A connector sees only what the tools return: the public airfoil library, your saved designs, and your quota.
It can add to your saved airfoils, wings and analyses — never delete or overwrite them. Deleting stays in the dashboard.
foil.tools never sees your conversation. Your assistant sends tool calls; we answer them.
Revoke access any time from Dashboard → API Keys. Revoking never touches your saved foils, designs or credits.
Anything an assistant hands you is a starting point for engineering judgement, not a substitute for it. Validate before you cut material.

Building your own client? See the API & MCP documentation.