yep

Shogi.Contracts/Api/Commands/MovePieceCommand.cs

@@ -7,6 +7,33 @@ namespace Shogi.Contracts.Api;
 
 public class MovePieceCommand : IValidatableObject
 {
+	/// <summary>
+	/// For serialization.
+	/// </summary>
+	public MovePieceCommand()
+	{
+		To = string.Empty;
+	}
+
+	/// <summary>
+	/// Move a piece on the board.
+	/// </summary>
+	public MovePieceCommand(string from, string to, bool isPromotion)
+	{
+		From = from;
+		To = to;
+		IsPromotion = isPromotion;
+	}
+
+	/// <summary>
+	/// Add a piece to the board from the hand.
+	/// </summary>
+	public MovePieceCommand(WhichPiece pieceFromHand, string to)
+	{
+		PieceFromHand = pieceFromHand;
+		To = to;
+	}
+
 	/// <summary>
 	/// Mutually exclusive with <see cref="From"/>.
 	/// Set this property to indicate moving a piece from the hand onto the board.
@@ -26,7 +53,7 @@ public class MovePieceCommand : IValidatableObject
 	[Required]
 	public string To { get; set; }
 	
-	public bool IsPromotion { get; set; }
+	public bool? IsPromotion { get; set; }
 
 	public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
 	{
@@ -34,6 +61,10 @@ public class MovePieceCommand : IValidatableObject
 		{
 			yield return new ValidationResult($"{nameof(PieceFromHand)} and {nameof(From)} are mutually exclusive properties.");
 		}
+		if (PieceFromHand.HasValue && IsPromotion.HasValue)
+		{
+			yield return new ValidationResult($"{nameof(PieceFromHand)} and {nameof(IsPromotion)} are mutually exclusive properties.");
+		}
 		if (!Regex.IsMatch(To, "[A-I][1-9]"))
 		{
 			yield return new ValidationResult($"{nameof(To)} must be a valid board position, between A1 and I9");