Remove fast-path cancellation check from CallTool (#48)

src/mcpdotnet/Configuration/McpServerBuilderExtensions.Tools.cs

@@ -1,6 +1,7 @@
 using System.ComponentModel;
 using System.Globalization;
 using System.Reflection;
+using System.Runtime.ExceptionServices;
 using System.Text.Json;
 using McpDotNet.Configuration;
 using McpDotNet.Protocol.Types;
@@ -171,18 +172,28 @@ public static partial class McpServerBuilderExtensions
 
     private static async Task<CallToolResponse> CallTool(RequestContext<CallToolRequestParams> request, MethodInfo method, CancellationToken cancellationToken)
     {
+        cancellationToken.ThrowIfCancellationRequested();
+
         var methodParameters = method.GetParameters();
         List<object?> parameters = ResolveParameters(request, methodParameters, cancellationToken);
 
-        if (cancellationToken.IsCancellationRequested)
-            return new CallToolResponse { Content = [new Content { Text = "Operation was cancelled" }] };
-
-        try
-        {
         using var scope = request.Server.ServiceProvider?.CreateScope();
         var objectInstance = CreateObjectInstance(method, scope?.ServiceProvider);
-            var result = method.Invoke(objectInstance, parameters.ToArray());
+        object? result;
-
+        try
+        {
+            const BindingFlags InvokeFlags =
+#if NET
+                BindingFlags.DoNotWrapExceptions |
+#endif
+                BindingFlags.Default;
+            result = method.Invoke(objectInstance, InvokeFlags, binder: null, parameters.ToArray(), culture: null);
+        }
+        catch (TargetInvocationException e) when (e.InnerException is not null)
+        {
+            ExceptionDispatchInfo.Capture(e.InnerException).Throw();
+            throw; // unreachable
+        }
 
         if (result is Task task)
         {
@@ -205,11 +216,6 @@ public static partial class McpServerBuilderExtensions
 
         return new CallToolResponse { Content = [new Content() { Text = result.ToString(), Type = "text" }] };
     }
-        catch (TargetInvocationException e)
-        {
-            throw new McpServerException(e.Message, e);
-        }
-    }
 
     private static List<object?> ResolveParameters(RequestContext<CallToolRequestParams> request, ParameterInfo[] methodParameters, CancellationToken cancellationToken)
     {