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ChessGrammar – API that detects tactical patterns in chess positions

ChessGrammar – API that detects tactical patterns in chess positions

by stevejvv·Feb 17, 2026·3 points·0 comments
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AI Analysis

●●SolidNiche GemBig Brain

Detects 10 tactical patterns without Stockfish—clever heuristics, tiny audience.

Strengths
  • •Two-phase detection (geometry + sequence confirmation) is a smart false-positive filter.
  • •No Stockfish runtime dependency keeps it lightweight and fast.
  • •Playground with bug-report button lowers friction for feedback and iteration.
Weaknesses
  • •Chess tooling is niche; limited TAM unless integrated into larger platforms.
  • •No evidence yet this outperforms or significantly differs from existing pattern libraries.
Target Audience

Chess engine developers, analysis tool builders, chess coaches, competitive players

Similar To

Lichess API · Chess.com analysis engine · Chessable pattern recognition

Post Description

I built an API that takes a FEN or PGN and returns every tactical pattern it finds — forks, pins, skewers, discovered attacks, back rank mates, and more (10 patterns total).

It uses a two-phase approach: fast geometric detection, then sequence confirmation to filter out false positives.

You can try it directly in the playground (no signup, no API key): https://chessgrammar.com/playground

Paste any FEN or a full PGN and see what it finds. The playground also has a bug report button if something looks wrong.

API docs: https://chessgrammar.com/docs

Built with Python (python-chess), deployed on Vercel. The engine runs custom heuristic algorithms — no Stockfish dependency at runtime.

Curious to hear feedback, especially from anyone who's worked on chess analysis tools.

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