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Using BetterChess in Claude

The connector gives Claude a real chess engine and the actual geometry of the board. You use it by asking — there is nothing to memorise.

The one rule: never for a live game against a person

Using an engine to choose your moves against a human opponent is cheating. On chess.com and Lichess it is detected and it gets your account closed — the fair play systems look for exactly this pattern, and “I only checked a few moves” is not a defence.

Fine, and what this is built for:

  • Games against a bot or computer opponent — Chess.com's fair play policy explicitly exempts these.
  • A game that is already over. Review it, find where it turned.
  • Any position you are studying, from a book, a puzzle, or your own head.
  • Openings, tactics, endgames — anything that is not a move you are about to play against someone.

Not fine, and we will not help with it: a live game against another person, anywhere — online, over the board, or correspondence. If you ask Claude for a move in a game against a human, it is instructed to ask who the opponent is and to decline while the answer is a person.

Setup

  1. In Claude, open Settings → Connectors → Add custom connector.
  2. Paste https://mcp.betterchess.co
  3. Sign in with your BetterChess account when Claude asks.

That is the whole setup. Nothing installs on your machine, and subscribing later lifts the cap on the connector you already added — you never reconnect it.

What to ask

There are no commands. Ask in plain language and Claude picks the right tool. These work as-is:

Analyse a position

Here is my position: rnbqkbnr/pppp1ppp/8/4p3/4P3/5N2/PPPP1PPP/RNBQKB1R b KQkq - 1 2. What is undefended, what attacks it, and what are the best moves?

Runs chess_analyse. You get the top moves with real evaluations, whose turn it is, whether that side is in check, undefended pieces and what attacks them, and the material balance.

Check one piece's reach

In that position, exactly which squares does the knight on f3 attack?

Runs chess_attacks. This is the one that stops confident nonsense about knights, pins and discovered attacks — the squares are computed, not recalled.

Review a finished game

Here is my PGN from a game I just finished. Where did I actually lose it? [paste PGN]

Runs chess_review (Pro). It replays the game and reports only the moves where the evaluation genuinely swung — the two moves that decided it, not forty small inaccuracies.

Sanity-check a move you are considering

I am studying this position and I want to play Ng5. Is that actually good, or is there a refutation? [paste FEN]

Analyses the position after your move, so you get the concrete refutation rather than an opinion. Use this while studying — not mid-game against a person.

What the connector actually gives Claude

ToolReturnsPlan
chess_analyseTop moves with evaluations, side to move, check, undefended pieces and their attackers, material balance.Free (daily budget)
chess_attacksThe exact squares a given piece attacks, and its type and colour.Free (daily budget)
chess_reviewEvery move in a finished game where the evaluation swung past a threshold, with the move played, the better move, and the position after.Pro

Getting better answers

  • Paste the position. A FEN, a PGN, or the moves so far. Describing it in words means Claude has to reconstruct it, and that is where mistakes come from.
  • Ask why, not just what. “What is the best move” gets you a move. “Why is that better than the obvious capture” gets you the thing that transfers to your next game.
  • Push back. If an explanation does not add up, say so and ask it to re-check against the board. The tools are there to be re-run.
  • Name your mistake. “I keep hanging pieces in the opening — go through this game and show me where” is a much better prompt than “review this game”.

Frequently asked

Do I need to install anything?

No. Paste the connector URL into Claude's connector settings and sign in with your BetterChess account. There is no terminal step, no config file and no local Stockfish. It works on the free Claude plan and on mobile.

Is there a /coach command?

Not yet. The connector gives Claude three tools — analysis, attack maps and game review — and you use them by asking in plain language. There is no slash command to install.

Can I use it while I am playing someone?

No. Using an engine to pick moves against a human opponent is cheating and will get your account banned on chess.com and Lichess. Against a bot, in a finished game, or on a position you are studying, it is fine — see the fair play section above.

What is the free limit?

A free account gets a daily analysis budget, which is enough to work through a game or study positions. Pro removes the cap for $5.99/month, cancel anytime.

Does Claude ever guess?

The board facts do not. Attackers, defenders, evaluations and legal moves are computed by the engine and handed to Claude as fact. Claude still writes the explanation around them, so if it ever says something that contradicts the numbers it returned, tell it — it will re-check.

Which position formats work?

FEN, PGN, or a plain list of moves from the start (e.g. e4 e5 Nf3 Nc6). Paste whichever you have.

Questions or something not working: info@betterchess.co. BetterChess is independent and not affiliated with Chess.com, Lichess or Anthropic; those names are their owners' trademarks. BetterChess is a practice tool — we make no guarantee of any rating result.

BetterChess

A chess engine for Claude. It reads your actual position and explains the why behind every move — grounded, never guessed.

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BetterChess is a practice tool. We make no guarantee that you'll reach 1800 or any rating. Improvement depends on your own practice, effort, and skill.
BetterChess is a connector for Claude. Claude and Anthropic are trademarks of Anthropic PBC. BetterChess is an independent product and is not affiliated with, endorsed by, or sponsored by Anthropic.
Engine analysis powered by Stockfish, © the Stockfish developers, licensed under the GPL v3 (source).
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