started working on player moves.

Shogi.Contracts/Api/Commands/CreateTokenResponse.cs

@@ -2,12 +2,9 @@
 
 namespace Shogi.Contracts.Api;
 
-  public class CreateTokenResponse
-  {
-      public Guid OneTimeToken { get; }
-
-      public CreateTokenResponse(Guid token)
-      {
-          OneTimeToken = token;
-      }
-  }
+public class CreateTokenResponse
+{
+	public string UserId { get; set; }
+	public string DisplayName { get; set; }
+	public Guid OneTimeToken { get; set; }
+}

Shogi.Contracts/Api/Commands/MovePieceCommand.cs

@@ -1,10 +1,46 @@
 using Shogi.Contracts.Types;
+using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
+using System.Text.RegularExpressions;
 
 namespace Shogi.Contracts.Api;
 
-  public class MovePieceCommand
-  {
-      [Required]
-      public Move Move { get; set; }
-  }
+public class MovePieceCommand : IValidatableObject
+{
+	/// <summary>
+	/// Mutually exclusive with <see cref="From"/>.
+	/// Set this property to indicate moving a piece from the hand onto the board.
+	/// </summary>
+	public WhichPiece? PieceFromHand { get; set; }
+	
+	/// <summary>
+	/// Board position notation, like A3 or G1
+	/// Mutually exclusive with <see cref="PieceFromHand"/>.
+	/// Set this property to indicate moving a piece from the board to another position on the board.
+	/// </summary>
+	public string? From { get; set; }
+
+	/// <summary>
+	/// Board position notation, like A3 or G1
+	/// </summary>
+	[Required]
+	public string To { get; set; }
+	
+	public bool IsPromotion { get; set; }
+
+	public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
+	{
+		if (PieceFromHand.HasValue && !string.IsNullOrWhiteSpace(From))
+		{
+			yield return new ValidationResult($"{nameof(PieceFromHand)} and {nameof(From)} are mutually exclusive properties.");
+		}
+		if (!Regex.IsMatch(To, "[A-I][1-9]"))
+		{
+			yield return new ValidationResult($"{nameof(To)} must be a valid board position, between A1 and I9");
+		}
+		if (!string.IsNullOrEmpty(From) && !Regex.IsMatch(From, "[A-I][1-9]"))
+		{
+			yield return new ValidationResult($"{nameof(From)} must be a valid board position, between A1 and I9");
+		}
+	}
+}

Shogi.Contracts/Socket/PlayerHasMovedMessage.cs

@@ -2,16 +2,16 @@
 
 namespace Shogi.Contracts.Socket;
 
-public class MoveResponse : ISocketResponse
+public class PlayerHasMovedMessage : ISocketResponse
 {
   public SocketAction Action { get; }
-  public string SessionName { get; set; } = string.Empty;
+  public string SessionName { get; set; }
   /// <summary>
   /// The player that made the move.
   /// </summary>
-  public string PlayerName { get; set; } = string.Empty;
+  public string PlayerName { get; set; }
 
-  public MoveResponse()
+  public PlayerHasMovedMessage()
   {
     Action = SocketAction.PieceMoved;
   }

Shogi.Contracts/Types/Move.cs

@@ -1,12 +0,0 @@
-namespace Shogi.Contracts.Types
-{
-  public class Move
-  {
-    public WhichPiece? PieceFromCaptured { get; set; }
-    /// <summary>Board position notation, like A3 or G1</summary>
-    public string? From { get; set; }
-    /// <summary>Board position notation, like A3 or G1</summary>
-    public string To { get; set; } = string.Empty;
-    public bool IsPromotion { get; set; }
-  }
-}