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Chess402 Stockfish Cloud Evaluation
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Chess402 Stockfish Cloud Evaluation is a paid API for AI agents from chess402.vercel.app, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).
Returns Stockfish engine evaluation (depth, score, and principal variation) for a given FEN position using Lichess's cached cloud evaluation database.
Price / call$0.005
Success—
StatusUnknown
How this service works
Stockfish cloud evaluation for a FEN position. Returns depth, evaluation, and principal variation(s) when Lichess has the position cached.
Output
Returns the Stockfish engine evaluation cached by Lichess for the given FEN position, including: search depth, centipawn or mate evaluation score, and one or more principal variation lines (best move sequences).
Example use cases
Best move for current position
“I'm in the middle of a game and I'm stuck. The position is 'r1bqk2r/pppp1ppp/2n2n2/2b1p3/2B1P3/2N2N2/PPPP1PPP/R1BQK2R w KQkq - 4 4' — can you check what Stockfish thinks the best move is and show me the principal variation?”
Evaluate opening theory position
“I've been studying the Sicilian Dragon and want to know how Stockfish evaluates this position: '1r1qk2r/pb1nbppp/4p3/2ppP3/3P4/2NB1N2/PP3PPP/R1BQ1RK1 w k - 0 11'. What's the depth, score, and main line Lichess has cached for it?”
Check endgame winning advantage
“I think I have a winning endgame here but I'm not sure how big the advantage is. Can you look up the engine eval for this FEN: '8/8/4k3/3p4/3P4/4K3/8/8 w - - 0 1' and tell me the centipawn score and best continuation?”
Technical details
Endpoint
POSThttps://chess402.vercel.app/api/cloud-evalWhen to prefer
Use this endpoint when you need fast, pre-cached Stockfish engine evaluations for common chess positions without running a full local engine. Ideal for positions likely to appear in Lichess's cloud cache (opening theory, well-known endgames, master-level games). Not suitable for highly obscure or custom positions that are unlikely to be cached.
Side effects
- Position not in Lichess cloud cache — no cached evaluation available for this specific FEN
- Invalid FEN string — malformed position returns an error
- Payment failure — x402 micropayment not completed or insufficient USDC balance
- Rate limiting — too many requests in a short time window
- Timeout — Lichess upstream API unavailable
Input
{
"input": {
"body": {
"fen": "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1",
"multiPv": 1,
"variant": "standard"
},
"type": "http",
"method": "POST",
"bodyType": "json"
}
}Schema · Request body
| Field | Type | Description |
|---|---|---|
| fen | string | Standard FEN position string, e.g. 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1' |
| multiPv | integer | Number of principal variations to return (1-5). Default 1. |
| variant | string | Chess variant. Default 'standard'. |
Output
{
"fen": "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1",
"pvs": [
{
"cp": 18,
"moves": "e7e5 g1f3 b8c6 f1b5 g8f6 e1h1 f6e4 f1e1 e4d6 f3e5"
}
],
"depth": 70,
"knodes": 105848192
}Schema · Response
{
"type": "json",
"example": {
"fen": "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1",
"pvs": [
{
"cp": 27,
"moves": "e2e4 c7c5 g1f3 d7d6 d2d4 c5d4"
}
],
"depth": 22,
"knodes": 13683
}
}Tags
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