{"uid":"cap_V7eyqHSHmqDTpJ5wAc7vp","slug":"chess402-vercel-app-6dc16e11","name":"Chess402 Stockfish Cloud Evaluation","description":"Stockfish cloud evaluation for a FEN position. Returns depth, evaluation, and principal variation(s) when Lichess has the position cached.","url":"https://chess402.vercel.app/api/cloud-eval","method":"POST","headers":{},"bodySchema":{"type":"object","properties":{"fen":{"type":"string","maxLength":100,"minLength":15,"description":"Standard FEN position string, e.g. 'rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1'"},"multiPv":{"type":"integer","maximum":5,"minimum":1,"description":"Number of principal variations to return (1-5). Default 1."},"variant":{"enum":["standard","chess960","crazyhouse","antichess","atomic","horde","kingOfTheHill","racingKings","threeCheck"],"type":"string","description":"Chess variant. Default 'standard'."}}},"responseSchema":{"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}},"example":{"request":{"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"}},"response":{"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}},"exampleRequest":{"fen":"rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1","multiPv":1,"variant":"standard"},"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"settled","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_FUc52jQnRuSXRHnNgdaG5","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Returns Stockfish engine evaluation (depth, score, and principal variation) for a given FEN position using Lichess's cached cloud evaluation database.","exampleAgentPrompt":"Can you get the Stockfish cloud evaluation for this FEN position: 'rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1'? I want to know the depth, score, and the principal variation Lichess has cached for it.","exampleUseCases":[{"title":"Best move for current position","prompt":"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?"},{"title":"Evaluate opening theory position","prompt":"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?"},{"title":"Check endgame winning advantage","prompt":"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?"}],"resultDescription":"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).","failureModes":["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"],"whenToPreferThis":"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.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-15T06:34:26.834Z","isFirstParty":false}