Trim "title" and "description" keywords from root-level schemas.

src/ModelContextProtocol/McpJsonUtilities.cs

@@ -2,6 +2,7 @@
 using ModelContextProtocol.Protocol;
 using System.Diagnostics.CodeAnalysis;
 using System.Text.Json;
+using System.Text.Json.Nodes;
 using System.Text.Json.Serialization;
 using System.Text.Json.Serialization.Metadata;
 
@@ -75,6 +76,25 @@ internal static bool IsValidMcpToolSchema(JsonElement element)
         return false; // No type keyword found.
     }
 
+    private static readonly string[] s_rootSchemaKeywordsToRemove = ["title", "description"];
+    internal static AIJsonSchemaCreateOptions DefaultSchemaCreateOptions { get; } = new()
+    {
+        TransformOptions = new()
+        {
+            TransformSchemaNode = static (ctx, node) =>
+            {
+                if (ctx.Path is [] && node is JsonObject obj)
+                {
+                    foreach (string keywordToRemove in s_rootSchemaKeywordsToRemove)
+                    {
+                        obj.Remove(keywordToRemove);
+                    }
+                }
+                return node;
+            },
+        }
+    };
+
     // Keep in sync with CreateDefaultOptions above.
     [JsonSourceGenerationOptions(JsonSerializerDefaults.Web,
         DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,

src/ModelContextProtocol/Server/AIFunctionMcpServerPrompt.cs

@@ -151,7 +151,7 @@ private static AIFunctionFactoryOptions CreateAIFunctionFactoryOptions(
                     return null;
                 }
             },
-            JsonSchemaCreateOptions = options?.SchemaCreateOptions,
+            JsonSchemaCreateOptions = options?.SchemaCreateOptions ?? McpJsonUtilities.DefaultSchemaCreateOptions,
         };
 
     /// <summary>Creates an <see cref="McpServerPrompt"/> that wraps the specified <see cref="AIFunction"/>.</summary>

src/ModelContextProtocol/Server/AIFunctionMcpServerTool.cs

@@ -160,7 +160,7 @@ private static AIFunctionFactoryOptions CreateAIFunctionFactoryOptions(
                     return null;
                 }
             },
-            JsonSchemaCreateOptions = options?.SchemaCreateOptions,
+            JsonSchemaCreateOptions = options?.SchemaCreateOptions ?? McpJsonUtilities.DefaultSchemaCreateOptions,
         };
 
     /// <summary>Creates an <see cref="McpServerTool"/> that wraps the specified <see cref="AIFunction"/>.</summary>

tests/ModelContextProtocol.Tests/Server/McpServerToolTests.cs

@@ -3,6 +3,7 @@
 using ModelContextProtocol.Protocol;
 using ModelContextProtocol.Server;
 using Moq;
+using System.ComponentModel;
 using System.Reflection;
 using System.Text.Json;
 using System.Text.Json.Serialization;
@@ -381,6 +382,23 @@ public async Task SupportsSchemaCreateOptions()
         );
     }
 
+    [Fact]
+    public void TrimsDescriptionAndTitleKeywordsFromRootSchema()
+    {
+        McpServerTool tool = McpServerTool.Create(Add);
+
+        Assert.Equal("My awesome adding tool", tool.ProtocolTool.Description);
+        Assert.False(tool.ProtocolTool.InputSchema.TryGetProperty("description", out _));
+        Assert.False(tool.ProtocolTool.InputSchema.TryGetProperty("title", out _));
+
+        // Preserves any nested description keywords
+        Assert.Equal("The first argument", tool.ProtocolTool.InputSchema.GetProperty("properties").GetProperty("a").GetProperty("description").GetString());
+        Assert.Equal("The second argument", tool.ProtocolTool.InputSchema.GetProperty("properties").GetProperty("b").GetProperty("description").GetString());
+
+        [Description("My awesome adding tool")]
+        static int Add([Description("The first argument")] int a , [Description("The second argument")] int b) => a + b;
+    }
+
     private sealed class MyService;
 
     private class DisposableToolType : IDisposable