Add ModelContextProtocol.Core package (#428)

src/ModelContextProtocol.Core/Protocol/ElicitationCapability.cs

@@ -0,0 +1,36 @@
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol;
+
+/// <summary>
+/// Represents the capability for a client to provide server-requested additional information during interactions.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This capability enables the MCP client to respond to elicitation requests from an MCP server.
+/// </para>
+/// <para>
+/// When this capability is enabled, an MCP server can request the client to provide additional information
+/// during interactions. The client must set a <see cref="ElicitationHandler"/> to process these requests.
+/// </para>
+/// </remarks>
+public class ElicitationCapability
+{
+    // Currently empty in the spec, but may be extended in the future.
+
+    /// <summary>
+    /// Gets or sets the handler for processing <see cref="RequestMethods.ElicitationCreate"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This handler function is called when an MCP server requests the client to provide additional
+    /// information during interactions. The client must set this property for the elicitation capability to work.
+    /// </para>
+    /// <para>
+    /// The handler receives message parameters and a cancellation token.
+    /// It should return a <see cref="ElicitResult"/> containing the response to the elicitation request.
+    /// </para>
+    /// </remarks>
+    [JsonIgnore]
+    public Func<ElicitRequestParams?, CancellationToken, ValueTask<ElicitResult>>? ElicitationHandler { get; set; }
+}