Address review feedback: rename field to s_camelCase and add test for unqualified types

- Rename FullyQualifiedFormatWithNullability to s_fullyQualifiedFormatWithNullability
- Add test for unqualified parameter type in source (using directive) to ensure
  the generator still produces fully qualified output

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

Author: Copilot

src/ModelContextProtocol.Analyzers/XmlToDescriptionGenerator.cs

@@ -23,7 +23,7 @@ public sealed class XmlToDescriptionGenerator : IIncrementalGenerator
     /// A display format that produces fully-qualified type names with "global::" prefix
     /// and includes nullability annotations.
     /// </summary>
-    private static readonly SymbolDisplayFormat FullyQualifiedFormatWithNullability =
+    private static readonly SymbolDisplayFormat s_fullyQualifiedFormatWithNullability =
         SymbolDisplayFormat.FullyQualifiedFormat.AddMiscellaneousOptions(
             SymbolDisplayMiscellaneousOptions.IncludeNullableReferenceTypeModifier);
 
@@ -133,7 +133,7 @@ private static MethodToGenerate ExtractMethodInfo(
             .Where(m => !m.IsKind(SyntaxKind.AsyncKeyword))
             .Select(m => m.Text);
         string modifiersStr = string.Join(" ", modifiers);
-        string returnType = methodSymbol.ReturnType.ToDisplayString(FullyQualifiedFormatWithNullability);
+        string returnType = methodSymbol.ReturnType.ToDisplayString(s_fullyQualifiedFormatWithNullability);
         string methodName = methodSymbol.Name;
 
         // Extract parameters
@@ -145,7 +145,7 @@ private static MethodToGenerate ExtractMethodInfo(
             var paramSyntax = i < parameterSyntaxList.Count ? parameterSyntaxList[i] : null;
 
             parameters[i] = new ParameterInfo(
-                ParameterType: param.Type.ToDisplayString(FullyQualifiedFormatWithNullability),
+                ParameterType: param.Type.ToDisplayString(s_fullyQualifiedFormatWithNullability),
                 Name: param.Name,
                 HasDescriptionAttribute: descriptionAttribute is not null && HasAttribute(param, descriptionAttribute),
                 XmlDescription: xmlDocs?.Parameters.TryGetValue(param.Name, out var pd) == true && !string.IsNullOrWhiteSpace(pd) ? pd : null,

tests/ModelContextProtocol.Analyzers.Tests/XmlToDescriptionGeneratorTests.cs

@@ -1777,6 +1777,68 @@ partial class Tools
         AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
     }
 
+    [Fact]
+    public void Generator_WithUnqualifiedTypeInSource_GeneratesFullyQualifiedTypeName()
+    {
+        // This test validates that even when the source code uses an unqualified type name
+        // (via a using directive), the generator still emits fully qualified type names.
+        // This is the exact scenario from the original issue.
+        var result = RunGenerator("""
+            using ModelContextProtocol.Server;
+            using System.ComponentModel;
+            using System.Threading.Tasks;
+            using MyApp.Actions;
+
+            namespace MyApp.Actions
+            {
+                public enum MyAction
+                {
+                    One,
+                    Two
+                }
+            }
+
+            namespace MyApp
+            {
+                [McpServerToolType]
+                public sealed partial class Tools
+                {
+                    /// <summary>Do a thing based on an action.</summary>
+                    /// <param name="action">The action to perform.</param>
+                    [McpServerTool]
+                    public async partial Task<string> DoThing(MyAction action)
+                        => await Task.FromResult("ok");
+                }
+            }
+            """);
+
+        Assert.True(result.Success);
+        Assert.Single(result.GeneratedSources);
+
+        // Even though the source uses unqualified "MyAction", the generated code should use
+        // the fully qualified "global::MyApp.Actions.MyAction"
+        var expected = $$"""
+            // <auto-generated/>
+            // ModelContextProtocol.Analyzers {{typeof(XmlToDescriptionGenerator).Assembly.GetName().Version}}
+
+            #pragma warning disable
+
+            using System.ComponentModel;
+            using ModelContextProtocol.Server;
+
+            namespace MyApp
+            {
+                partial class Tools
+                {
+                    [Description("Do a thing based on an action.")]
+                    public partial global::System.Threading.Tasks.Task<string> DoThing([Description("The action to perform.")] global::MyApp.Actions.MyAction action);
+                }
+            }
+            """;
+
+        AssertGeneratedSourceEquals(expected, result.GeneratedSources[0].SourceText.ToString());
+    }
+
     private GeneratorRunResult RunGenerator([StringSyntax("C#-test")] string source, params string[] expectedDiagnosticIds)
     {
         var syntaxTree = CSharpSyntaxTree.ParseText(source);