Add example documentation and update README with availability info

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

Author: Copilot

src/ModelContextProtocol.SourceGenerators/EXAMPLE.md

@@ -0,0 +1,70 @@
+# Source Generator Example
+
+This example demonstrates how to use the XmlToDescriptionGenerator source generator.
+
+## Without Source Generator (Traditional Approach)
+
+```csharp
+using ModelContextProtocol.Server;
+using System.ComponentModel;
+
+[McpServerToolType]
+public class WeatherTools
+{
+    /// <summary>
+    /// Get the current weather for a location.
+    /// </summary>
+    [McpServerTool]
+    [Description("Get the current weather for a location.")]  // Duplication!
+    public static string GetWeather(string location)
+    {
+        return $"Weather for {location}: Sunny, 72°F";
+    }
+}
+```
+
+## With Source Generator (Recommended)
+
+```csharp
+using ModelContextProtocol.Server;
+
+[McpServerToolType]
+public partial class WeatherTools
+{
+    /// <summary>
+    /// Get the current weather for a location.
+    /// </summary>
+    [McpServerTool]
+    public static partial string GetWeather(string location)
+    {
+        return $"Weather for {location}: Sunny, 72°F";
+    }
+}
+```
+
+The source generator automatically creates a partial method declaration with the `[Description]` attribute:
+
+```csharp
+// <auto-generated/>
+#nullable enable
+
+using System.ComponentModel;
+using ModelContextProtocol.Server;
+
+namespace YourNamespace;
+
+public partial class WeatherTools
+{
+    [Description("Get the current weather for a location.")]
+    public static partial string GetWeather(string location);
+}
+```
+
+## Key Changes Required
+
+1. Make the class `partial`
+2. Make the method `partial`
+3. Remove any existing `[Description]` attribute
+4. Keep your XML documentation comments
+
+The Description attribute will be automatically generated from your XML `<summary>` element!

src/ModelContextProtocol.SourceGenerators/README.md

@@ -65,6 +65,11 @@ public partial class MyTools
 - 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
+- Your project must reference `ModelContextProtocol.Core` directly (the source generator is distributed with this package)
+
+### Availability
+
+The source generator is distributed as part of the `ModelContextProtocol.Core` NuGet package and will be automatically available when you reference that package in your project.
 
 ### Notes