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Is there an online chess evaluation engine with a REST API? I'd like to be able to send a game or position (with castling ability presumably) to a simple REST API and get back the positional evaluation from a reasonably strong engine.

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  • I don't think so.
    – SmallChess
    Mar 20, 2016 at 8:07
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    I think a very simple purpose would be to allow developers to use it to create apps. On the other hand the API provider can use the requests for deep learning networks. Win-Win. Mar 20, 2016 at 17:57
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    It is part of an evil plan to create the world's strongest chess player Mar 20, 2016 at 18:18
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    @PeterCotton There's no free lunch. You can't expect anyone giving you anything like that. Please learn how to code a proper engine for the web.
    – SmallChess
    Mar 20, 2016 at 23:58
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    Nobody expects the inquisition. analysis.cpuchess.com is pretty close, but no API Mar 21, 2016 at 0:29

2 Answers 2

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+100

The project https://github.com/noobpwnftw/chessdb provides an API for getting engine evaluations including also the PV, with the FEN of a position as input.

E.g., try an example from the readme:

https://www.chessdb.cn/cdb.php?action=querypv&board=rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR%20w%20KQkq%20-%200%201&json=1

The response I got is:

{"status":"ok","score":8,"depth":39,"pv":["e2e4","c7c5","d2d4","c5d4","g1f3","e7e5","c2c3","b8c6","f1c4","g8f6","f3g5","d7d5","e4d5","c6a5","c4b5","c8d7","d1e2","f8d6","b2b4","h7h6","g5f3","e8g8","b4a5","d4d3","e2b2","f6d5","b1d2","d7b5","b2b5","d5c3","b5d3","d6b4","d3d8","f8d8","a5a6","b7a6","a2a3","b4a5","e1f1"],"pvSAN":["e4","c5","d4","cxd4","Nf3","e5","c3","Nc6","Bc4","Nf6","Ng5","d5","exd5","Na5","Bb5+","Bd7","Qe2","Bd6","b4","h6","Nf3","O-O","bxa5","d3","Qb2","Nxd5","Nbd2","Bxb5","Qxb5","Nxc3","Qxd3","Bb4","Qxd8","Rfxd8","a6","bxa6","a3","Ba5","Kf1"]}
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    It is essentially functioning as an opening book api and not able to evaluate unknown positions on-the-fly. e.g. chessdb.cn/cdb.php?action=querypv&board=8/7K/P2P4/1b1k3p/…
    – prusswan
    Jul 6, 2019 at 17:44
  • That's what I infer too. Funny comment at bottom "Expect no further documentation except this one but the code should be self-explanatory", even though there isn't a single line explaining what it is :) Oct 22, 2021 at 2:32
  • Interesting find. I awarded the bounty although this question remains open. I'm rather surprised that in 2021 the world doesn't have a chess position evaluation API ! Oct 25, 2021 at 13:06
  • On the contrary, I would rather be surprised if there existed one. Who would provide such an API and all the necessary computational resources and why?
    – Hauptideal
    Jul 18 at 22:48
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It is pointless to have a rest API for random position evals which have to be precomputed for near-instant response. In that case you might as well ask for an opening book. There are a few sites that with opening book querying tools, which are pretty close.

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    Why do you say that? You can squeeze plenty into a reasonable REST API timeout. Oct 17, 2021 at 15:39

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