Add ModelContextProtocol.Core package (#428)

src/ModelContextProtocol.Core/Protocol/Argument.cs

@@ -0,0 +1,29 @@
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents an argument used in completion requests to provide context for auto-completion functionality.
+/// </summary>
+/// <remarks>
+/// This class is used when requesting completion suggestions for a particular field or parameter.
+/// See the <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/">schema</see> for details.
+/// </remarks>
+public class Argument
+{
+    /// <summary>
+    /// Gets or sets the name of the argument being completed.
+    /// </summary>
+    [JsonPropertyName("name")]
+    public string Name { get; set; } = string.Empty;
+
+    /// <summary>
+    /// Gets or sets the current partial text value for which completion suggestions are requested.
+    /// </summary>
+    /// <remarks>
+    /// This represents the text that has been entered so far and for which completion
+    /// options should be generated.
+    /// </remarks>
+    [JsonPropertyName("value")]
+    public string Value { get; set; } = string.Empty;
+}