[MCP] Fixed issue with deserialization of prompt settings (#9085)

Author: glen-84

src/All.slnx

@@ -194,6 +194,7 @@
     <Project Path="HotChocolate/Adapters/src/Fusion.Adapters.OpenApi/HotChocolate.Fusion.Adapters.OpenApi.csproj" />
   </Folder>
   <Folder Name="/HotChocolate/Adapters/test/">
+    <Project Path="HotChocolate/Adapters/test/Adapters.Mcp.Core.Tests/HotChocolate.Adapters.Mcp.Core.Tests.csproj" />
     <Project Path="HotChocolate/Adapters/test/Adapters.Mcp.Packaging.Tests/HotChocolate.Adapters.Mcp.Packaging.Tests.csproj" />
     <Project Path="HotChocolate/Adapters/test/Adapters.Mcp.Tests/HotChocolate.Adapters.Mcp.Tests.csproj" />
     <Project Path="HotChocolate/Adapters/test/Adapters.OpenApi.Packaging.Tests/HotChocolate.Adapters.OpenApi.Packaging.Tests.csproj" />

src/HotChocolate/Adapters/Adapters.slnx

@@ -15,6 +15,7 @@
   </Folder>
   <Folder Name="/test/" />
   <Folder Name="/test/Adapters.Mcp.Tests/">
+    <Project Path="test\Adapters.Mcp.Core.Tests\HotChocolate.Adapters.Mcp.Core.Tests.csproj" />
     <Project Path="test\Adapters.Mcp.Packaging.Tests\HotChocolate.Adapters.Mcp.Packaging.Tests.csproj" />
     <Project Path="test\Adapters.Mcp.Tests\HotChocolate.Adapters.Mcp.Tests.csproj" />
   </Folder>

src/HotChocolate/Adapters/src/Adapters.Mcp.Core/Serialization/McpSettingsSerializerContext.cs

@@ -6,5 +6,6 @@ namespace HotChocolate.Adapters.Mcp.Serialization;
 [JsonSerializable(typeof(McpToolSettingsDto))]
 [JsonSourceGenerationOptions(
     PropertyNamingPolicy = JsonKnownNamingPolicy.CamelCase,
-    DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull)]
+    DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+    AllowOutOfOrderMetadataProperties = true)]
 internal partial class McpSettingsSerializerContext : JsonSerializerContext;

src/HotChocolate/Adapters/test/Adapters.Mcp.Core.Tests/HotChocolate.Adapters.Mcp.Core.Tests.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <Import Project="$([MSBuild]::GetPathOfFileAbove('Xunit2.Directory.Build.props', '$(MSBuildThisFileDirectory)..\'))" />
+
+  <PropertyGroup>
+    <AssemblyName>HotChocolate.Adapters.Mcp.Core.Tests</AssemblyName>
+    <RootNamespace>HotChocolate.Adapters.Mcp.Core</RootNamespace>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Adapters.Mcp.Core\HotChocolate.Adapters.Mcp.Core.csproj" />
+  </ItemGroup>
+
+</Project>

src/HotChocolate/Adapters/test/Adapters.Mcp.Core.Tests/Serialization/McpPromptSettingsSerializerTests.cs

@@ -0,0 +1,37 @@
+using System.Text.Json;
+using HotChocolate.Adapters.Mcp.Serialization;
+
+namespace HotChocolate.Adapters.Mcp.Core.Serialization;
+
+public sealed class McpPromptSettingsSerializerTests
+{
+    [Fact]
+    public void Parse_WithPolymorphicMessages_ShouldSucceed()
+    {
+        // arrange
+        var document =
+            JsonDocument.Parse(
+                """
+                {
+                    "messages": [
+                        {
+                            "role": "user",
+                            "content": {
+                                "text": "Get the person",
+                                "type": "text"
+                            }
+                        }
+                    ]
+                }
+                """);
+
+        // act
+        var settings = McpPromptSettingsSerializer.Parse(document);
+
+        // assert
+        var message = Assert.Single(settings.Messages);
+        Assert.Equal("user", message.Role);
+        var content = Assert.IsType<McpPromptSettingsTextContentDto>(message.Content);
+        Assert.Equal("Get the person", content.Text);
+    }
+}