Complete source generator implementation with README and fix analyzer loading

Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>

Author: Copilot

src/ModelContextProtocol.Core/ModelContextProtocol.Core.csproj

@@ -54,4 +54,17 @@
                       ReferenceOutputAssembly="false" />
   </ItemGroup>
 
+  <!-- Direct analyzer reference for build-time source generation -->
+  <ItemGroup>
+    <Analyzer Include="$(ArtifactsDir)bin\ModelContextProtocol.SourceGenerators\netstandard2.0\ModelContextProtocol.SourceGenerators.dll" />
+  </ItemGroup>
+
+  <!-- Package the analyzer DLL into the NuGet package -->
+  <ItemGroup>
+    <None Include="$(ArtifactsDir)bin\ModelContextProtocol.SourceGenerators\netstandard2.0\ModelContextProtocol.SourceGenerators.dll" 
+          Pack="true" 
+          PackagePath="analyzers/dotnet/cs" 
+          Visible="false" />
+  </ItemGroup>
+
 </Project>

src/ModelContextProtocol.SourceGenerators/README.md

@@ -0,0 +1,73 @@
+# ModelContextProtocol.SourceGenerators
+
+This project contains source generators for the Model Context Protocol C# SDK.
+
+## XmlToDescriptionGenerator
+
+This source generator automatically creates `Description` attributes from XML documentation comments for partial methods tagged with `[McpServerTool]`.
+
+### How it works
+
+When you write a partial method with:
+1. An `[McpServerTool]` attribute
+2. XML documentation comments (specifically a `<summary>` tag)
+3. NO existing `[Description]` attribute
+
+The generator will create a partial method declaration with a `[Description]` attribute containing the text from the XML `<summary>` element.
+
+### Example Usage
+
+**Your code:**
+```csharp
+using ModelContextProtocol.Server;
+using System.ComponentModel;
+
+[McpServerToolType]
+public partial class MyTools
+{
+    /// <summary>
+    /// This tool echoes the input message back to the user.
+    /// </summary>
+    [McpServerTool]
+    public static partial string Echo(string message)
+    {
+        return $"Echo: {message}";
+    }
+}
+```
+
+**Generated code:**
+```csharp
+// <auto-generated/>
+#nullable enable
+
+using System.ComponentModel;
+using ModelContextProtocol.Server;
+
+namespace YourNamespace;
+
+public partial class MyTools
+{
+    [Description("This tool echoes the input message back to the user.")]
+    public static partial string Echo(string message);
+}
+```
+
+### Benefits
+
+- **Reduces duplication**: You don't need to write both XML comments AND Description attributes
+- **Single source of truth**: XML comments are used for both documentation and runtime tool descriptions
+- **Automatic synchronization**: Changes to XML comments are automatically reflected in the Description attributes
+
+### Requirements
+
+- Your method must be marked as `partial`
+- Your method must have the `[McpServerTool]` attribute
+- Your method must have XML documentation comments with a `<summary>` tag
+- Your method must NOT already have a `[Description]` attribute
+
+### Notes
+
+- The generator only extracts text from the `<summary>` element
+- Multi-line summaries are combined into a single line
+- Only partial methods with implementations (method bodies) are supported