Chess Analysis API

Chess analysis that explains the why, not just the what. Position evaluation, game review, and personalized coaching — ready for your app.

Get Started See Examples

Try It — Ask Chessy

Natural Language Q&AAsk any question about a position or game and get a direct answer

Positions & GamesDeep position evaluation and full game review with move-by-move annotation

Highly CustomizableSkill levels, coaching styles, and personalities — adapt output to any user

Fast & ReliablePosition analysis in seconds, full game review with coaching narrative

Position Analysis

Deep position evaluation with AI coaching

Send any FEN position and get deep evaluation, best move, tactical detection, and natural language explanations. Optionally ask a specific question about the position.

−0.25

+0.25

Evaluation

+0.25

Best Move

Ng5

Assessment

Slight White

Right now your e4 pawn is hanging. Black has a direct hit on it, so you must play something that either defends it or creates a stronger threat. That's why Ng5 is attractive: it gains tempo by hitting sensitive squares (especially f7/e6) and makes Black respond instead of just winning your pawn. Your light-squared bishop and queenside pieces are still asleep, so the plan is simple: use Ng5 to seize initiative, then finish development quickly (O-O, d3, Nc3). Overall it's a small plus for White because you can gain tempi and develop with threats.

JSON

{
  "response": "Right now your e4 pawn is hanging — Black has a direct hit on it — so you must play something that either defends it or creates a stronger threat. That's why Ng5 is attractive: it gains tempo by hitting sensitive squares (especially f7/e6)...",
  "best_move": "Ng5",
  "best_move_uci": "f3g5",
  "evaluation": 0.25,
  "assessment": "slight white",
  "fen": "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"
}

−0.20

+0.20

Evaluation

+0.20

Best Move

Ng5

Assessment

Equal

Question: “What should I play here and why?”Play Ng5. It hits f7 and forces Black to respond, so you win a tempo while also making sure your pieces stay active and coordinated. After that, keep it simple: castle quickly and finish development before you start any real attacking.

JSON

{
  "response": "Play Ng5. It hits f7 and forces Black to respond, so you win a tempo while also making sure your pieces stay active and coordinated. After that, keep it simple: castle quickly and finish development before you start any real attacking.",
  "best_move": "Ng5",
  "best_move_uci": "f3g5",
  "evaluation": 0.20,
  "assessment": "equal",
  "fen": "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"
}

Built to Adapt

Same position, completely different coaching

Skill levels, personalities, and question types — every dimension of the coaching output is customizable through the API.

+3.88

Evaluation

+3.88

Best Move

exd5

Assessment

Decisive

Beginner800 ELO

This position is screaming for a tactic: exd5! Your e-pawn takes on d5 and immediately attacks both the bishop on c6 and the knight on e6, so Black can't save everything without losing time or material. The center is the whole story here — once you crack it open, your pieces come alive.

Do: Play exd5 to win tempo

Avoid: Passive moves like h3

Key idea: Attack two pieces at once

Request

{
  "position": "r2q1rk1/...",
  "player_rating": 800
}

Game Analysis

Full game analysis with move-by-move annotation

Upload a PGN and get move-by-move classification, accuracy percentages, error detection, and a full narrative overview.

95.8%

White Accuracy

93.9%

Black Accuracy

32.3

White ACPL

42.6

Black ACPL

Philidor Defense

Opening

Move Timeline

33 half-moves

Excellent

Good

Book

Inaccuracy

Mistake

Blunder

Overview

White seized a decisive initiative with 7. Qb3 and 16. Qb8+, while Black's missteps around 9... b5 and 10... cxb5 loosened the position. The game featured 3 brilliant moves and a sharp finish culminating in Rd8#. White's only significant error was 15. Bxd7+, which threw away 3.3 pawns of advantage — Bxf6 would have maintained pressure. Despite this, the brilliant 16. Qb8+ recovery sealed the win.

Key Errors

Blunder

Move 15. Bxd7+ — Loses 3.3 pawns of advantage. Bxf6 maintains the pin on Black's g-pawn and keeps pressure on the kingside.

Mistake

Move 10... cxb5 — Opens lines for White's attack. Better was Qb4+, which forces concessions and creates immediate counterplay instead of loosening the queenside structure.

Mistake

Move 6... Nf6 — Passive development that allowed White to consolidate with Qb3and intensify pressure. Better was Qf6, directly challenging White's control.

JSON

{
  "response": "Key tactical ideas: the game featured frequent tactical motifs like exchanges and piece activity...",
  "overview": {
    "summary_sentence": "White seized a decisive initiative with 7. Qb3...",
    "narrative_text": "The opening pieces unfold with White steering..."
  },
  "game_summary": {
    "white_accuracy": 95.8,
    "black_accuracy": 93.9,
    "white_acpl": 32.3,
    "black_acpl": 42.6,
    "total_moves": 33
  },
  "moves": [ // 33 move objects],
  "turning_points": [ // 7 key moments],
  "white_mistakes": [ // errors with review],
  "study_plan": {
    "strengths": [...],
    "tactics_work": "Train recognizing forced continuations..."
  }
}

Game Q&A

Natural Language

Question: “What were the key tactical ideas in this game?”The game featured frequent tactical motifs like exchanges and piece activity turning into material swings. The big swing at 15. Bxd7+ shifted momentum, and X-rays, interpositions, and skewers dictated the tempo throughout. Move 7. Qb3 was brilliant — it immediately created mating threats and shifted the evaluation in White's favor. The finale with 16. Qb8+ followed by Rd8# demonstrated how piece coordination converts an attack into checkmate.

Request

{
  "pgn": "1. e4 e5 2. Nf3 d6 3. d4 Bg4 4. dxe5 Bxf3 ...",
  "question": "What were the key tactical ideas in this game?",
  "player_color": "white"
}

Note: When you include a question, the response field directly addresses your question using the full analysis context. All other fields (overview, moves, errors, game_summary) remain available in the same response.

Get Started

Integrate chess analysis in minutes

One API key. Two endpoints. Position evaluation, game annotation, and AI coaching.

cURL

curl -X POST https://api.chessvia.ai/analyze_position \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"position": "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1", "question": "What should I play?", "player_rating": 1200}'

Get in touch

Tell us about your project and we'll set you up with an API key.

Custom integrations available. Reach out to learn more.

Chess Analysis API

Chess analysis that explains the why, not just the what. Position evaluation, game review, and personalized coaching — ready for your app.

Get Started See Examples

Try It — Ask Chessy

Natural Language Q&AAsk any question about a position or game and get a direct answer

Positions & GamesDeep position evaluation and full game review with move-by-move annotation

Highly CustomizableSkill levels, coaching styles, and personalities — adapt output to any user

Fast & ReliablePosition analysis in seconds, full game review with coaching narrative

Position Analysis

Deep position evaluation with AI coaching

Send any FEN position and get deep evaluation, best move, tactical detection, and natural language explanations. Optionally ask a specific question about the position.

−0.25

+0.25

Evaluation

+0.25

Best Move

Ng5

Assessment

Slight White

JSON

{
  "response": "Right now your e4 pawn is hanging — Black has a direct hit on it — so you must play something that either defends it or creates a stronger threat. That's why Ng5 is attractive: it gains tempo by hitting sensitive squares (especially f7/e6)...",
  "best_move": "Ng5",
  "best_move_uci": "f3g5",
  "evaluation": 0.25,
  "assessment": "slight white",
  "fen": "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"
}

−0.20

+0.20

Evaluation

+0.20

Best Move

Ng5

Assessment

Equal

JSON

{
  "response": "Play Ng5. It hits f7 and forces Black to respond, so you win a tempo while also making sure your pieces stay active and coordinated. After that, keep it simple: castle quickly and finish development before you start any real attacking.",
  "best_move": "Ng5",
  "best_move_uci": "f3g5",
  "evaluation": 0.20,
  "assessment": "equal",
  "fen": "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"
}

Built to Adapt

Same position, completely different coaching

Skill levels, personalities, and question types — every dimension of the coaching output is customizable through the API.

+3.88

Evaluation

+3.88

Best Move

exd5

Assessment

Decisive

Beginner800 ELO

Do: Play exd5 to win tempo

Avoid: Passive moves like h3

Key idea: Attack two pieces at once

Request

{
  "position": "r2q1rk1/...",
  "player_rating": 800
}

Game Analysis

Full game analysis with move-by-move annotation

Upload a PGN and get move-by-move classification, accuracy percentages, error detection, and a full narrative overview.

95.8%

White Accuracy

93.9%

Black Accuracy

32.3

White ACPL

42.6

Black ACPL

Philidor Defense

Opening

Move Timeline

33 half-moves

Excellent

Good

Book

Inaccuracy

Mistake

Blunder

Overview

Key Errors

Blunder

Move 15. Bxd7+ — Loses 3.3 pawns of advantage. Bxf6 maintains the pin on Black's g-pawn and keeps pressure on the kingside.

Mistake

Move 10... cxb5 — Opens lines for White's attack. Better was Qb4+, which forces concessions and creates immediate counterplay instead of loosening the queenside structure.

Mistake

Move 6... Nf6 — Passive development that allowed White to consolidate with Qb3and intensify pressure. Better was Qf6, directly challenging White's control.

JSON

{
  "response": "Key tactical ideas: the game featured frequent tactical motifs like exchanges and piece activity...",
  "overview": {
    "summary_sentence": "White seized a decisive initiative with 7. Qb3...",
    "narrative_text": "The opening pieces unfold with White steering..."
  },
  "game_summary": {
    "white_accuracy": 95.8,
    "black_accuracy": 93.9,
    "white_acpl": 32.3,
    "black_acpl": 42.6,
    "total_moves": 33
  },
  "moves": [ // 33 move objects],
  "turning_points": [ // 7 key moments],
  "white_mistakes": [ // errors with review],
  "study_plan": {
    "strengths": [...],
    "tactics_work": "Train recognizing forced continuations..."
  }
}

Game Q&A

Natural Language

Request

{
  "pgn": "1. e4 e5 2. Nf3 d6 3. d4 Bg4 4. dxe5 Bxf3 ...",
  "question": "What were the key tactical ideas in this game?",
  "player_color": "white"
}

Get Started

Integrate chess analysis in minutes

One API key. Two endpoints. Position evaluation, game annotation, and AI coaching.

cURL

curl -X POST https://api.chessvia.ai/analyze_position \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"position": "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1", "question": "What should I play?", "player_rating": 1200}'

Get in touch

Tell us about your project and we'll set you up with an API key.

Custom integrations available. Reach out to learn more.