diff --git a/src/Libraries/Microsoft.Extensions.AI.Abstractions/CHANGELOG.md b/src/Libraries/Microsoft.Extensions.AI.Abstractions/CHANGELOG.md
index cc911fd64bb..526072374c4 100644
--- a/src/Libraries/Microsoft.Extensions.AI.Abstractions/CHANGELOG.md
+++ b/src/Libraries/Microsoft.Extensions.AI.Abstractions/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 - Added new `ChatResponseFormat.ForJsonSchema` overloads that export a JSON schema from a .NET type.
 - Updated `TextReasoningContent` to include `ProtectedData` for representing encrypted/redacted content.
+- Fixed `MinLength`/`MaxLength`/`Length` attribute mapping in nullable string properties during schema export.
 
 ## 9.9.0
 
diff --git a/src/Libraries/Microsoft.Extensions.AI.OpenAI/CHANGELOG.md b/src/Libraries/Microsoft.Extensions.AI.OpenAI/CHANGELOG.md
index 4d858edeb89..a50aea8dea3 100644
--- a/src/Libraries/Microsoft.Extensions.AI.OpenAI/CHANGELOG.md
+++ b/src/Libraries/Microsoft.Extensions.AI.OpenAI/CHANGELOG.md
@@ -2,7 +2,8 @@
 
 ## NOT YET RELEASED
 
-- Added M.E.AI to OpenAI conversions for response format types
+- Added M.E.AI to OpenAI conversions for response format types.
+- Added `ResponseTool` to `AITool` conversions.
 
 ## 9.9.0-preview.1.25458.4
 
diff --git a/src/Libraries/Microsoft.Extensions.AI.OpenAI/MicrosoftExtensionsAIResponsesExtensions.cs b/src/Libraries/Microsoft.Extensions.AI.OpenAI/MicrosoftExtensionsAIResponsesExtensions.cs
index ca4bfd3f736..c632f3c45c7 100644
--- a/src/Libraries/Microsoft.Extensions.AI.OpenAI/MicrosoftExtensionsAIResponsesExtensions.cs
+++ b/src/Libraries/Microsoft.Extensions.AI.OpenAI/MicrosoftExtensionsAIResponsesExtensions.cs
@@ -93,4 +93,46 @@ public static OpenAIResponse AsOpenAIResponse(this ChatResponse response, ChatOp
             previousResponseId: options?.ConversationId,
             instructions: options?.Instructions);
     }
+
+    /// <summary>Adds the <see cref="ResponseTool"/> to the list of <see cref="AITool"/>s.</summary>
+    /// <param name="tools">The list of <see cref="AITool"/>s to which the provided tool should be added.</param>
+    /// <param name="tool">The <see cref="ResponseTool"/> to add.</param>
+    /// <remarks>
+    /// <see cref="ResponseTool"/> does not derive from <see cref="AITool"/>, so it cannot be added directly to a list of <see cref="AITool"/>s.
+    /// Instead, this method wraps the provided <see cref="ResponseTool"/> in an <see cref="AITool"/> and adds that to the list.
+    /// The <see cref="IChatClient"/> returned by <see cref="OpenAIClientExtensions.AsIChatClient(OpenAIResponseClient)"/> will
+    /// be able to unwrap the <see cref="ResponseTool"/> when it processes the list of tools and use the provided <paramref name="tool"/> as-is.
+    /// </remarks>
+    public static void Add(this IList<AITool> tools, ResponseTool tool)
+    {
+        _ = Throw.IfNull(tools);
+
+        tools.Add(AsAITool(tool));
+    }
+
+    /// <summary>Creates an <see cref="AITool"/> to represent a raw <see cref="ResponseTool"/>.</summary>
+    /// <param name="tool">The tool to wrap as an <see cref="AITool"/>.</param>
+    /// <returns>The <paramref name="tool"/> wrapped as an <see cref="AITool"/>.</returns>
+    /// <remarks>
+    /// <para>
+    /// The returned tool is only suitable for use with the <see cref="IChatClient"/> returned by
+    /// <see cref="OpenAIClientExtensions.AsIChatClient(OpenAIResponseClient)"/> (or <see cref="IChatClient"/>s that delegate
+    /// to such an instance). It is likely to be ignored by any other <see cref="IChatClient"/> implementation.
+    /// </para>
+    /// <para>
+    /// When a tool has a corresponding <see cref="AITool"/>-derived type already defined in Microsoft.Extensions.AI,
+    /// such as <see cref="AIFunction"/>, <see cref="HostedWebSearchTool"/>, <see cref="HostedMcpServerTool"/>, or
+    /// <see cref="HostedFileSearchTool"/>, those types should be preferred instead of this method, as they are more portable,
+    /// capable of being respected by any <see cref="IChatClient"/> implementation. This method does not attempt to
+    /// map the supplied <see cref="ResponseTool"/> to any of those types, it simply wraps it as-is:
+    /// the <see cref="IChatClient"/> returned by <see cref="OpenAIClientExtensions.AsIChatClient(OpenAIResponseClient)"/> will
+    /// be able to unwrap the <see cref="ResponseTool"/> when it processes the list of tools.
+    /// </para>
+    /// </remarks>
+    public static AITool AsAITool(this ResponseTool tool)
+    {
+        _ = Throw.IfNull(tool);
+
+        return new OpenAIResponsesChatClient.ResponseToolAITool(tool);
+    }
 }
diff --git a/src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIResponsesChatClient.cs b/src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIResponsesChatClient.cs
index 36bf4ca68b4..e2fbfdf3f84 100644
--- a/src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIResponsesChatClient.cs
+++ b/src/Libraries/Microsoft.Extensions.AI.OpenAI/OpenAIResponsesChatClient.cs
@@ -414,6 +414,10 @@ private ResponseCreationOptions ToOpenAIResponseCreationOptions(ChatOptions? opt
             {
                 switch (tool)
                 {
+                    case ResponseToolAITool rtat:
+                        result.Tools.Add(rtat.Tool);
+                        break;
+
                     case AIFunctionDeclaration aiFunction:
                         result.Tools.Add(ToResponseTool(aiFunction, options));
                         break;
@@ -877,4 +881,11 @@ private static void AddAllMcpFilters(IList<string> toolNames, McpToolFilter filt
             filter.ToolNames.Add(toolName);
         }
     }
+
+    /// <summary>Provides an <see cref="AITool"/> wrapper for a <see cref="ResponseTool"/>.</summary>
+    internal sealed class ResponseToolAITool(ResponseTool tool) : AITool
+    {
+        public ResponseTool Tool => tool;
+        public override string Name => Tool.GetType().Name;
+    }
 }
diff --git a/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIConversionTests.cs b/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIConversionTests.cs
index b919592da4d..7724ad98360 100644
--- a/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIConversionTests.cs
+++ b/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIConversionTests.cs
@@ -316,7 +316,7 @@ public async Task AsChatResponse_ConvertsOpenAIStreamingChatCompletionUpdates()
             updates.Add(update);
         }
 
-        ChatResponse response = updates.ToChatResponse();
+        var response = updates.ToChatResponse();
 
         Assert.Equal("id", response.ResponseId);
         Assert.Equal(ChatFinishReason.ToolCalls, response.FinishReason);
@@ -1176,6 +1176,31 @@ public void AsOpenAIResponse_WithBothModelIds_PrefersChatResponseModelId()
         Assert.Equal("response-model-id", openAIResponse.Model);
     }
 
+    [Fact]
+    public void ListAddResponseTool_AddsToolCorrectly()
+    {
+        Assert.Throws<ArgumentNullException>("tools", () => ((IList<AITool>)null!).Add(ResponseTool.CreateWebSearchTool()));
+        Assert.Throws<ArgumentNullException>("tool", () => new List<AITool>().Add((ResponseTool)null!));
+
+        Assert.Throws<ArgumentNullException>("tool", () => ((ResponseTool)null!).AsAITool());
+
+        ChatOptions options;
+
+        options = new()
+        {
+            Tools = new List<AITool> { ResponseTool.CreateWebSearchTool() },
+        };
+        Assert.Single(options.Tools);
+        Assert.NotNull(options.Tools[0]);
+
+        options = new()
+        {
+            Tools = [ResponseTool.CreateWebSearchTool().AsAITool()],
+        };
+        Assert.Single(options.Tools);
+        Assert.NotNull(options.Tools[0]);
+    }
+
     private static async IAsyncEnumerable<T> CreateAsyncEnumerable<T>(IEnumerable<T> source)
     {
         foreach (var item in source)
diff --git a/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIResponseClientTests.cs b/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIResponseClientTests.cs
index 9175b6afd57..866e43e172d 100644
--- a/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIResponseClientTests.cs
+++ b/test/Libraries/Microsoft.Extensions.AI.OpenAI.Tests/OpenAIResponseClientTests.cs
@@ -825,8 +825,10 @@ public async Task MultipleOutputItems_NonStreaming()
         Assert.Equal(36, response.Usage.TotalTokenCount);
     }
 
-    [Fact]
-    public async Task McpToolCall_ApprovalNotRequired_NonStreaming()
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public async Task McpToolCall_ApprovalNotRequired_NonStreaming(bool rawTool)
     {
         const string Input = """
             {
@@ -1031,13 +1033,16 @@ public async Task McpToolCall_ApprovalNotRequired_NonStreaming()
         using HttpClient httpClient = new(handler);
         using IChatClient client = CreateResponseClient(httpClient, "gpt-4o-mini");
 
+        AITool mcpTool = rawTool ?
+            ResponseTool.CreateMcpTool("deepwiki", new("https://mcp.deepwiki.com/mcp"), toolCallApprovalPolicy: new McpToolCallApprovalPolicy(GlobalMcpToolCallApprovalPolicy.NeverRequireApproval)).AsAITool() :
+            new HostedMcpServerTool("deepwiki", "https://mcp.deepwiki.com/mcp")
+            {
+                ApprovalMode = HostedMcpServerToolApprovalMode.NeverRequire,
+            };
+
         ChatOptions chatOptions = new()
         {
-            Tools = [new HostedMcpServerTool("deepwiki", "https://mcp.deepwiki.com/mcp")
-                {
-                    ApprovalMode = HostedMcpServerToolApprovalMode.NeverRequire,
-                }
-            ],
+            Tools = [mcpTool],
         };
 
         var response = await client.GetResponseAsync("Tell me the path to the README.md file for Microsoft.Extensions.AI.Abstractions in the dotnet/extensions repository", chatOptions);