# Stockfish MCP: a real chess engine for Claude

> A Stockfish MCP server gives Claude a real chess engine to call. The open-source options, what their output looks like, and how Chess Coach uses Stockfish.

- URL: https://thechesscoach.netlify.app/answers/stockfish-mcp-server/
- Updated: 2026-11-04
- Author: Ignacio Soler

A Stockfish MCP server lets Claude call the Stockfish chess engine as a tool, so evaluations and best moves come from real search instead of the model's guesswork. Open-source options exist on GitHub, such as [sonirico/mcp-stockfish](https://github.com/sonirico/mcp-stockfish) and [indulge/stockfish-mcp-server](https://github.com/indulge/stockfish-mcp-server). You run them on your own computer next to a [Stockfish](https://stockfishchess.org/) binary, which is free and open source under the [GPL-3.0 license](https://github.com/official-stockfish/Stockfish) (as of October 2026).

MCP, the [Model Context Protocol](https://modelcontextprotocol.io/docs/getting-started/intro), is the open standard that lets assistants like Claude use outside tools. A Stockfish MCP server is one of those tools: a position goes in, the engine's numbers come out.

## Stockfish MCP servers at a glance

Checked on October 25, 2026, from each project's README. Stars and dates change.

| Project | How Claude talks to it | Language | Notes | License |
|---|---|---|---|---|
| [sonirico/mcp-stockfish](https://github.com/sonirico/mcp-stockfish) | Sends raw UCI commands (`position fen`, `go depth`) as text | Go | Up to 10 engine sessions at once by default; stdio or HTTP mode; 16 stars | MIT |
| [indulge/stockfish-mcp-server](https://github.com/indulge/stockfish-mcp-server) | Separate tools: `analyze_position`, `get_best_move`, `get_legal_moves`, `apply_moves` and more | Python (python-chess, FastMCP) | Stateless, every call takes a FEN; Stockfish binary not bundled | Not stated |
| [Chess Coach](/connect/) (ours) | Asks for a game review or a position check in plain language | Remote server | Stockfish runs on our server; fetches your games; interactive board | Free plan, paid plans |

UCI is the text protocol chess engines speak, and FEN is a one-line text description of a position. GitHub has several more small Stockfish MCP repositories, most with no stars or documentation yet, so these two are the ones with clear READMEs.

The setup is the same for both: download Stockfish from the [official releases](https://github.com/official-stockfish/Stockfish), install the server and add it to Claude Desktop's configuration file. The MCP documentation explains [how to connect local servers](https://modelcontextprotocol.io/docs/develop/connect-local-servers).

## Claude and a chess engine: why the tool matters

Claude doesn't have a chess engine inside. A language model predicts text, so it can sound sure about a position it has misread, and in long games it can lose track of where the pieces are. Public leaderboards rank language models far below any engine; we collected the numbers in [ChatGPT vs Stockfish](/answers/chatgpt-vs-stockfish/) and [Can Claude play chess?](/answers/can-claude-play-chess/).

Stockfish works the other way. It searches ahead through the legal moves and scores the positions it reaches. What it doesn't do is explain. That makes the pair useful: the engine decides, the model translates.

## What Stockfish returns, and what a beginner needs

Here's a well-known trap from the opening. Black's knight has jumped to the center, leaving the pawn in front of it apparently free. White's knight can grab it.

> **Taking the pawn looks free, but trading knights keeps White slightly better**
> Position (FEN): `r1bqkbnr/pppp1ppp/8/4p3/2BnP3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4`
> Played: Nxe5 — Knight takes the pawn, but Black's queen comes out with a double attack
> Better: Nxd4 — Knight takes the knight: a trade that keeps White better

Asked about this position, Stockfish answers with lines like `+1.35 4. Nxd4 exd4 5. O-O Nf6 6. d3 d5`. That's complete and correct, and it means little to most players. In plain words: trading knights keeps White slightly better. Grabbing the pawn instead lets Black's queen come out and attack two things at once (a double attack: one move, two threats), the knight in the center and the pawn protecting White's king. The position becomes about equal. That's the gap a Stockfish MCP server alone leaves: you get the numbers, and Claude still has to turn them into words without getting the position wrong.

## How Chess Coach uses Stockfish

Chess Coach is a remote MCP server for Claude and ChatGPT. There's nothing to install: in Claude, connect [Chess Coach from its directory listing](https://claude.ai/directory/chess-coach) ([setup steps](/connect/)) and sign in with your email or Google.

- **Stockfish on our server.** `review_game` analyzes a finished Chess.com or Lichess game, a game link or a pasted PGN. `analyze_position` checks any position or line you want to explore.
- **Moves described from the rules.** Each move's description (what it captures, what it attacks, what it leaves undefended) is computed, so Claude explains facts instead of reconstructing the board.
- **A board in the chat.** Key moments ①②③, red and green arrows, an evaluation graph, "Why?" buttons and Practice mistakes.

The Free plan includes one in-depth review and 30 position checks a day; Plus is $3.99/month and Pro $7.99/month. Chess Coach never helps with games in progress. Chess Coach is available in [Claude’s directory](https://claude.ai/directory/chess-coach) and [OpenAI’s plugin directory](https://chatgpt.com/plugins/plugin_asdk_app_6ad9e00bd14481918e1bfc260a358e03). Open its listing, install it and sign in with your Chess Coach account.

If you'd rather build your own setup, pair a local Stockfish server with a data server for your site: see [Chess.com MCP servers](/answers/chess-com-mcp-server/) and [Lichess MCP](/answers/lichess-mcp-server/). Chess Coach is not affiliated with the Stockfish project, Chess.com, Lichess, Anthropic or OpenAI.

## FAQ

### Does Claude have a built-in chess engine?

No. Claude is a language model: it reads positions as text and judges them by pattern. To get engine-accurate evaluations it needs a tool such as a Stockfish MCP server or a connector that runs Stockfish.

### Is there a free Stockfish MCP server?

Yes. sonirico/mcp-stockfish (MIT license) and indulge/stockfish-mcp-server are open source on GitHub, and Stockfish itself is free under the GPL-3.0 license. You install and run them on your own computer.

### Do I need to download Stockfish separately?

For the local servers, usually yes. indulge/stockfish-mcp-server says the binary isn't bundled because it's over 100 MB and includes a download script; sonirico/mcp-stockfish expects a Stockfish binary on your path or set in an environment variable.

### Can a Stockfish MCP server review my Chess.com or Lichess games?

Not by itself: it analyzes positions you give it as FEN, it doesn't fetch games. Chess Coach combines both, finding your finished Chess.com and Lichess games and reviewing them with Stockfish on our server.

## Related

- [Chess MCP server for Claude and ChatGPT: Chess Coach](https://thechesscoach.netlify.app/connect.md)
- [ChatGPT vs Stockfish: who wins at chess, and why](https://thechesscoach.netlify.app/answers/chatgpt-vs-stockfish.md)
- [Chess.com MCP server: your options for Claude (2026)](https://thechesscoach.netlify.app/answers/chess-com-mcp-server.md)
- [Lichess MCP server: what it does in Claude (2026)](https://thechesscoach.netlify.app/answers/lichess-mcp-server.md)
- [Can Claude play chess? What it can and can't do (2026)](https://thechesscoach.netlify.app/answers/can-claude-play-chess.md)