Your engine is making the move MOVE. Do not echo moves from xboard with this command; send only new moves made by the engine.
For the actual move text from your chess engine (in place of MOVE above), your move should be either
in coordinate notation (e.g., e2e4, e7e8q) with castling indicated by the King's two-square move (e.g., e1g1), or
in Standard Algebraic Notation (SAN) as defined in the Portable Game Notation standard (e.g, e4, Nf3, O-O, cxb5, Nxe4, e8=Q), with the extension piece@square (e.g., P@f7) to handle piece placement in bughouse and crazyhouse.
xboard itself also accepts some variants of SAN, but for compatibility with non-xboard interfaces, it is best not to rely on this behavior.
Warning: Even though all versions of this protocol specification have indicated that xboard accepts SAN moves, some non-xboard interfaces are known to accept only coordinate notation. See the Idioms section for more information on the known limitations of some non-xboard interfaces. It should be safe to send SAN moves if you receive a "protover 2" (or later) command from the interface, but otherwise it is best to stick to coordinate notation for maximum compatibility. An even more conservative approach would be for your engine to send SAN to the interface only if you have set feature san=1 (which causes the interface to send SAN to you) and have received "accepted san" in reply.
Your engine is making the move MOVE. Do not echo moves from xboard with this command; send only new moves made by the engine. For the actual move text from your chess engine (in place of MOVE above), your move should be either
in coordinate notation (e.g., e2e4, e7e8q) with castling indicated by the King's two-square move (e.g., e1g1), or in Standard Algebraic Notation (SAN) as defined in the Portable Game Notation standard (e.g, e4, Nf3, O-O, cxb5, Nxe4, e8=Q), with the extension piece@square (e.g., P@f7) to handle piece placement in bughouse and crazyhouse. xboard itself also accepts some variants of SAN, but for compatibility with non-xboard interfaces, it is best not to rely on this behavior.
Warning: Even though all versions of this protocol specification have indicated that xboard accepts SAN moves, some non-xboard interfaces are known to accept only coordinate notation. See the Idioms section for more information on the known limitations of some non-xboard interfaces. It should be safe to send SAN moves if you receive a "protover 2" (or later) command from the interface, but otherwise it is best to stick to coordinate notation for maximum compatibility. An even more conservative approach would be for your engine to send SAN to the interface only if you have set feature san=1 (which causes the interface to send SAN to you) and have received "accepted san" in reply.