{
  "markdown": "# OhMyWind ⛵\n\n> **Talk to your LLM. Cast off with confidence.**\n>\n> OhMyWind turns any MCP-capable assistant (Claude, Le Chat, Cursor, Goose,\n> Zed, Continue) into a sailing planner. Ask in plain language, anywhere in\n> the world: get a per-leg ETA, a 1‑5 complexity score, and a deep-link to\n> the full plan. On the French Atlantic coast it goes further, swapping the\n> global current model for the SHOM Atlas C2D and MARC PREVIMER atlases.\n> Free, keyless, open source.\n\n[![CI](https://github.com/qdonnars/ohmywind/actions/workflows/ci.yml/badge.svg)](https://github.com/qdonnars/ohmywind/actions/workflows/ci.yml)\n\n[**ohmywind.fr**](https://ohmywind.fr) · [MCP endpoint](https://mcp.ohmywind.fr/mcp) · [AGPL-3.0](LICENSE) + [trademark](TRADEMARK.md)\n\n> [!WARNING]\n> **Decision-support tool, not a navigation instrument.** OhMyWind does not\n> replace the official marine forecast from your national weather service,\n> up-to-date charts, or the skipper's judgement. Forecast models are sometimes\n> wrong: you remain responsible for your passage.\n\n![OhMyWind passage plan rendered in the web app](docs/screenshots/plan.png)\n\n---\n\n## Try it in 30 seconds\n\n**1.** Open your MCP client and add the endpoint:\n\n```\nhttps://mcp.ohmywind.fr/mcp\n```\n\n**2.** Ask, in your own words:\n\n> *\"Demain matin, Marseille → Porquerolles, sur un Sun Odyssey 36. Bonne\n> idée ? Combien de temps et c'est tendu comment ?\"*\n\n**3.** Your assistant calls the OhMyWind tools and answers in plain language.\nOn hosts that support the [MCP Apps spec](https://modelcontextprotocol.io/extensions/client-matrix)\n(Claude, Claude Desktop, ChatGPT, VS Code Copilot, Goose, Postman, MCPJam) you\nalso get a live, interactive widget: the [ohmywind.fr](https://ohmywind.fr)\nplan view rendered inline. On hosts that don't (Cursor, Le Chat, terminal),\nthe assistant hands you the same plan as an [ohmywind.fr](https://ohmywind.fr)\ndeep-link. No account. No API key. No credit card.\n\n> **First time with MCP?** It takes 2 minutes. Pick your client on\n> [modelcontextprotocol.io/clients](https://modelcontextprotocol.io/clients),\n> then follow the\n> [remote-server quickstart](https://modelcontextprotocol.io/docs/develop/connect-remote-servers).\n> Claude Desktop users can start with the\n> [user quickstart](https://modelcontextprotocol.io/quickstart/user). In Le Chat,\n> add it under **Connectors → Add connector → Custom MCP connector** and paste\n> the endpoint above.\n\n### If your client only speaks stdio\n\nSome hosts cannot reach a remote MCP server directly yet. Bridge it with\n[`mcp-remote`](https://www.npmjs.com/package/mcp-remote), which runs locally\nand forwards to the endpoint:\n\n```json\n{\n  \"mcpServers\": {\n    \"ohmywind\": {\n      \"command\": \"npx\",\n      \"args\": [\"-y\", \"mcp-remote\", \"https://mcp.ohmywind.fr/mcp\"]\n    }\n  }\n}\n```\n\nNothing else to configure: **no account, no API key, no OAuth, no credit\ncard.** A client that asks you for credentials is guessing rather than reading\nthe server, and you can leave those fields empty.\n\n### Ask it something real\n\nThree prompts, each exercising a different tool:\n\n- *\"Quels bateaux tu connais ? J'ai un First 27.\"* maps your boat to a polar\n  archetype. The assistant chooses from the descriptions; there is no\n  server-side lookup table.\n- *\"Le vent au cap Sicié samedi après-midi ?\"* returns wind and sea at one\n  point, AROME first, in knots.\n- *\"Meilleur créneau cette semaine pour Marseille → Porquerolles ?\"* walks\n  every hourly departure up to 14 days out and compares them in one call.\n\n## Why OhMyWind\n\n|                              |                                                                                              |\n|------------------------------|----------------------------------------------------------------------------------------------|\n| 🆓 **Free, keyless**         | Wind & sea via [Open-Meteo](https://open-meteo.com) (CC BY 4.0). No account, no API key.     |\n| 🌍 **Works anywhere**        | Global models (ECMWF, GFS) cover any coast. Over France, AROME 1.3 km takes over and catches thermals, mistral, tramontane. |\n| ⛵ **Boat-aware**             | Seven archetypes from 20 ft trailer-cruisers to bluewater 50-footers, real polars, an `efficiency` parameter for trim and crew level. |\n| 🗓️ **Window-aware**           | One call sweeps a 14-day departure range and lets your LLM pick the calmest weekend slot, no math by hand. |\n| 🔌 **Client-agnostic**        | One HTTP MCP endpoint. Works in Claude Desktop, Le Chat, Cursor, Goose, Zed, Continue, …     |\n| 🖼️ **Rich on supporting hosts** | On Claude / ChatGPT / VS Code Copilot / Goose, an interactive widget renders inline via [MCP Apps](https://modelcontextprotocol.io/extensions/client-matrix). Other hosts fall back to a clean text summary + deep-link. |\n| 🛠️ **Open source, AGPL**      | Self-host on Fly, Modal, or your own VPS: `mcp-core` is deployment-agnostic. The HF Space is one wrapper among many. Fork it under your own name and icons, see [TRADEMARK.md](TRADEMARK.md). |\n\n## What the LLM sees\n\nFour MCP tools, all async, all keyless:\n\n| Tool                      | What it does                                                              |\n|---------------------------|---------------------------------------------------------------------------|\n| `list_boat_archetypes`    | Seven descriptive archetypes; the LLM maps \"Sun Odyssey 36\" → `cruiser_30ft` itself. |\n| `get_marine_forecast`     | Wind + sea around a point/window, multi-model.                            |\n| `plan_passage`            | End-to-end: per-leg timing + 1‑5 complexity + ohmywind.fr deep-link, in one call. Pass `latest_departure` to compare every hourly window up to 14 days out, and the LLM picks the calmest slot. |\n| `read_me`                 | Returns OhMyWind's calculation methodology. Call it when the user asks how things are computed. |\n\n`plan_passage` declares an MCP Apps UI resource (`ui://openwind/plan-passage`)\non its `_meta`. Hosts that support [MCP Apps](https://modelcontextprotocol.io/extensions/client-matrix)\nrender the live `ohmywind.fr/plan?…` view in a sandboxed iframe automatically,\nwith no host-specific CSS and no vendor lock-in. Hosts without MCP Apps support\nsilently get the structured payload + the `openwind_url` deep-link.\n\n## Architecture\n\n```\npackages/\n├── data-adapters/   # pure domain logic (forecast adapters, polars, routing, complexity)\n├── mcp-core/        # FastMCP server (cloud-agnostic, no Gradio, no HF deps)\n├── hf-space/        # Docker wrapper for Hugging Face Spaces (Starlette + uvicorn)\n└── web/             # React 19 + Vite app deployed to Cloudflare Pages (ohmywind.fr)\n```\n\n`mcp-core` stays deployment-agnostic. Re-deploying on Fly, Modal, or a VPS is\na different `Dockerfile` calling the same `build_server()`. See\n[docs/architecture.md](docs/architecture.md).\n\n## Run locally\n\n```bash\n# Tests + lint (data-adapters & mcp-core, Python via uv)\ncd packages/mcp-core\nuv sync --all-extras\nuv run pytest -x -q\nuv run ruff check .\n\n# Local HTTP MCP smoke\ncd packages/hf-space\nuv run python app.py   # serves :7860, point any MCP client at /mcp\n\n# Web app (ohmywind.fr)\ncd packages/web\nnpm install\nnpm run dev            # vite dev server\nnpm run build          # outputs packages/web/dist\n```\n\n## V1 scope\n\nWind, sea (`Hs` max), per-leg ETA, 1–5 complexity. Tides and currents ignored\non the Med (negligible). No automatic routing optimisation: the LLM and the\nhuman stay in the loop. Roadmap and scope decisions live in a `plan/` directory kept\nlocal to the working copy, not published here.\n\n## Calculation method\n\nDefaults below are what the MCP server uses unless overridden by tool parameters.\nImplementation: [`packages/data-adapters/src/openwind_data/routing/passage.py`](packages/data-adapters/src/openwind_data/routing/passage.py).\n\n### Polar speed model\n\n- 7 archetypes (`cruiser_20ft`, `cruiser_25ft`, `cruiser_30ft`, `cruiser_40ft`, `cruiser_50ft`, `racer_cruiser`, `catamaran_40ft`), each with an ORC-style polar in [`packages/data-adapters/src/openwind_data/routing/polars/`](packages/data-adapters/src/openwind_data/routing/polars/).\n- Lookup is **bilinear interpolation** in (TWS, TWA), clamped at grid edges.\n- TWA is symmetric `[0°, 180°]` only, no port/starboard distinction.\n\n### Boat speed adjustments\n\n- **Efficiency factor (default 0.75).** ORC polars are theoretical maxima. Real cruising loses ~25% (sail trim, comfort margins, helmsman, untracked currents). Override per call: `0.85` racing, `0.75` cruising, `0.65` loaded family cruising, `0.55` heavy seas / fouled hull.\n- **VMG / tacking correction.** When the route's TWA is below the boat's optimal upwind angle (typically ~42-48°), the simulator assumes the sailor tacks. Effective speed toward destination is `polar(optimal_TWA) × cos(optimal_TWA − route_TWA)`. At dead upwind this reduces to `polar(opt) × cos(opt) ≈ polar / √2`; at TWA=20° with opt=45° the reduction is only `cos(25°) ≈ 0.91`.\n- **Wave derate (opt-in).** `max(0.5, 1 − 0.05 × Hs^1.75 × cos²(TWA/2))`. Disabled by default; sea state feeds the warning bar rather than slowing the boat.\n- **Minimum boat speed.** 0.5 kn floor, prevents division blow-up in extreme stalls.\n\n### Timing\n\n- **Single-pass approximation.** A 6 kn heuristic estimates segment mid-times, then real polar speeds are computed at each mid-time's actual wind. No convergence iteration. Bias is bounded by the Mediterranean's multi-hour wind correlation length.\n- Routes are split into ~10 nm sub-segments by default for per-segment weather sampling. Drop to 5 nm for tight coastal work; raise to 20 nm for long offshore legs.\n\n### Compare-windows mode\n\n`plan_passage` accepts an optional `latest_departure` that turns the call into a window comparison: it walks N hourly departures over the same route and returns one entry per window. Weather is fetched once (cache prewarm), simulations are in-memory. Hard cap: 14 d × 24 h = 336 windows. The LLM (not the server) picks the best option qualitatively.\n\n### Currents: why SHOM and MARC, not just the global model\n\nOpen-Meteo's SMOC current field is global and 8 km wide. On the French Atlantic\ncoast that is not enough: the passes where a current decides the passage are\nnarrower than one grid cell. The adapter therefore stacks two coastal sources on\ntop of it, the SHOM Atlas C2D and the MARC PREVIMER atlases, and falls back to\nSMOC outside their coverage.\n\nThe gap is measured, not assumed. Over 120 SHOM-covered points and 24 hourly\nsnapshots each (2880 pairs, seed 42), pairwise speed disagreement in knots:\n\n| Pair | mean | median | p95 | max |\n|---|---:|---:|---:|---:|\n| SHOM vs MARC | 0.293 | 0.177 | 0.951 | 2.879 |\n| SHOM vs SMOC | 0.549 | 0.385 | 1.606 | 3.907 |\n| MARC vs SMOC | 0.490 | 0.347 | 1.460 | 4.068 |\n\nRead the first row against the second. The MARC harmonic engine tracks the SHOM\nreference about twice as closely as the global model does, and direction tells\nthe same story (7.3° median between SHOM and MARC, 23.6° between SHOM and SMOC).\nA p95 spread of 1.6 kn against a 5 kn boat is the difference between carrying a\npass and fighting it. Note what this is not: SMOC adds wind-driven and Stokes\ncomponents that SHOM's harmonic atlas leaves out, so the second row mixes\npredictor skill with a genuine physical difference and is not a pure error\nmetric. The third row is the one that decided the 5 GB payload was worth\nshipping.\n\nFull report, per-atlas breakdown and method:\n[`docs/bench/currents_3way_2026-05-10_1818.md`](docs/bench/currents_3way_2026-05-10_1818.md).\n\n### Mediterranean defaults\n\n- **Tides ignored.** < 40 cm in the Med, negligible vs. forecast uncertainty.\n- **Currents ignored.** Liguro-Provençal current too weak / variable for V1.\n- **Wind model.** AROME 1.3 km (≤48 h horizon, captures thermals and local winds). Auto-falls back to ICON-EU (≤5 d) → ECMWF IFS 0.25° (≤10 d) → GFS (≤16 d) when the passage extends past AROME.\n- **Wave model.** Open-Meteo Marine (significant Hs, period, direction).\n\n### What's not modelled (V1)\n\n- No automatic routing optimisation: the LLM and human stay in the loop on departure choice.\n- No coastal acceleration zones (capes, peninsulas): the caller adds intermediate waypoints.\n- No port/starboard polar asymmetry, no spinnaker-specific curves, no hull condition modelling beyond the `efficiency` knob.\n\n## Credits\n\nTidal currents on the French Atlantic coast: SHOM Atlas C2D and MARC PREVIMER\n(Ifremer). The prebuilt atlases live in a **private** HF dataset, and stay\nprivate: the raw MARC NetCDF is used under a no-redistribution commitment, so\nthe Space pulls them with a read token rather than shipping them here. Building\nwithout that token is supported and falls back to the global current model.\n\nWind & sea: [Open-Meteo](https://open-meteo.com/) (CC BY 4.0). Hosting:\n[Hugging Face Spaces](https://huggingface.co/spaces). Map tiles on\n[ohmywind.fr](https://ohmywind.fr): [CARTO](https://carto.com/) /\n[OpenStreetMap](https://www.openstreetmap.org/copyright).\n\n## License and trademark\n\nCode: [AGPL-3.0-or-later](LICENSE). That covers everything under `packages/`,\nthe web app, the MCP server and the data adapters alike. Forking and\nredistribution stay free; if you serve a modified instance over the network\n(your own MCP endpoint, a derived web app), you must publish its source.\nVersions up to commit `f276c3c` were MIT-licensed and remain so: see\n[COPYING.MIT](COPYING.MIT).\n\nTwo things the AGPL licence does **not** cover:\n\n- **The name \"OhMyWind\"**, filed as a trademark at the INPI, the French\n  industrial property office.\n- **The visual identity** (logo, app icons), which stays under copyright.\n\nForks are welcome. Publish them under your own name and your own icons. The\nfull policy, and what counts as a technical figure rather than brand identity,\nis in [TRADEMARK.md](TRADEMARK.md).\n\nData is licensed separately by each provider: Open-Meteo forecasts under\nCC BY 4.0, SHOM Atlas C2D under Licence Ouverte Etalab 2.0, MARC PREVIMER under\na no-redistribution commitment on the raw NetCDF. The per-source table lives in\n[docs/methodologie.md](docs/methodologie.md).\n",
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