user9856: 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. 

user33243: I was searching for one as well and this seems to do it: chess-analysis-api.
And here is an example URL: https://chess-analysis-api.herokuapp.com/analysis?fen=1r1q1rk1/pp4pn/3p3p/2p1nb2/2P2B2/2NP3P/PP2P1B1/R3QRK1%20b%20-%20-%201%2015&depth=20&multiPv=2

user15415: 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"]}


9856: <p>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. </p>
 33243: <p>I was searching for one as well and this seems to do it: <a href="https://github.com/Orivoir/chess-analysis-api-package" rel="nofollow noreferrer">chess-analysis-api</a>.</p>
<p>And here is an example URL: <a href="https://chess-analysis-api.herokuapp.com/analysis?fen=1r1q1rk1/pp4pn/3p3p/2p1nb2/2P2B2/2NP3P/PP2P1B1/R3QRK1%20b%20-%20-%201%2015&amp;depth=20&amp;multiPv=2" rel="nofollow noreferrer">https://chess-analysis-api.herokuapp.com/analysis?fen=1r1q1rk1/pp4pn/3p3p/2p1nb2/2P2B2/2NP3P/PP2P1B1/R3QRK1%20b%20-%20-%201%2015&amp;depth=20&amp;multiPv=2</a></p>
 15415: <p>The project <a href="https://github.com/noobpwnftw/chessdb" rel="nofollow noreferrer">https://github.com/noobpwnftw/chessdb</a> provides an API for getting engine evaluations including also the PV, with the FEN of a position as input.</p>

<p>E.g., try an example from the readme:</p>

<p><a href="https://www.chessdb.cn/cdb.php?action=querypv&amp;board=rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR%20w%20KQkq%20-%200%201&amp;json=1" rel="nofollow noreferrer">https://www.chessdb.cn/cdb.php?action=querypv&amp;board=rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR%20w%20KQkq%20-%200%201&amp;json=1</a></p>

<p>The response I got is:</p>

<pre><code>{"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"]}
</code></pre>
