Overview

ChessGrammar is a REST API that detects tactical patterns in chess positions. Send a FEN string or a PGN game, get back every tactic with its trigger move, material gain, and forcing sequence.

Quick Start

curl -X POST https://chessgrammar.com/api/v1/extract \
  -H "Content-Type: application/json" \
  -d '{"fen": "6k1/5p1p/4p3/4q3/3n4/2Q3P1/PP1N1P1P/6K1 b - - 3 37"}'

Response:

{
  "tactics": [
    {
      "pattern": "fork",
      "color": "black",
      "trigger_move": "d4e2",
      "key_squares": ["e2"],
      "target_squares": ["g1", "c3"],
      "gain": 700,
      "is_mate": false,
      "sequence": ["d4e2", "g1g2", "e2c3"]
    },
    {
      "pattern": "discovered_attack",
      "color": "black",
      "trigger_move": "d4e2",
      "key_squares": ["e5", "d4"],
      "target_squares": ["c3"],
      "gain": 700,
      "is_mate": false,
      "sequence": ["d4e2", "g1g2", "e2c3", "b2c3"]
    }
  ],
  "count": 2,
  "performance_ms": 177.7,
  "fen": "6k1/5p1p/..."
}

How It Works

Send a position (FEN) or a game (PGN). The engine scans for tactical patterns and confirms each one by calculating the actual material gain through best play. You receive the pattern type, trigger move, target squares, material gain, and the winning sequence of moves.

Endpoints

Rate Limits

The public API is rate-limited to 30 requests per minute per IP. No API key required.