diff --git a/dotnet/src/AutoGen.OpenAI.V1/Middleware/OpenAIChatRequestMessageConnector.cs b/dotnet/src/AutoGen.OpenAI.V1/Middleware/OpenAIChatRequestMessageConnector.cs
index f1bea485c..3587d1b0d 100644
--- a/dotnet/src/AutoGen.OpenAI.V1/Middleware/OpenAIChatRequestMessageConnector.cs
+++ b/dotnet/src/AutoGen.OpenAI.V1/Middleware/OpenAIChatRequestMessageConnector.cs
@@ -335,7 +335,10 @@ public class OpenAIChatRequestMessageConnector : IMiddleware, IStreamingMiddlewa
 
         var toolCall = message.ToolCalls.Select((tc, i) => new ChatCompletionsFunctionToolCall(tc.ToolCallId ?? $"{tc.FunctionName}_{i}", tc.FunctionName, tc.FunctionArguments));
         var textContent = message.GetContent() ?? string.Empty;
-        var chatRequestMessage = new ChatRequestAssistantMessage(textContent) { Name = message.From };
+
+        // don't include the name field when it's tool call message.
+        // fix https://github.com/microsoft/autogen/issues/3437
+        var chatRequestMessage = new ChatRequestAssistantMessage(textContent);
         foreach (var tc in toolCall)
         {
             chatRequestMessage.ToolCalls.Add(tc);
diff --git a/dotnet/src/AutoGen.OpenAI/Middleware/OpenAIChatRequestMessageConnector.cs b/dotnet/src/AutoGen.OpenAI/Middleware/OpenAIChatRequestMessageConnector.cs
index 2297d123b..fd55a1350 100644
--- a/dotnet/src/AutoGen.OpenAI/Middleware/OpenAIChatRequestMessageConnector.cs
+++ b/dotnet/src/AutoGen.OpenAI/Middleware/OpenAIChatRequestMessageConnector.cs
@@ -322,7 +322,10 @@ public class OpenAIChatRequestMessageConnector : IMiddleware, IStreamingMiddlewa
 
         var toolCallParts = message.ToolCalls.Select((tc, i) => ChatToolCall.CreateFunctionToolCall(tc.ToolCallId ?? $"{tc.FunctionName}_{i}", tc.FunctionName, tc.FunctionArguments));
         var textContent = message.GetContent() ?? null;
-        var chatRequestMessage = new AssistantChatMessage(toolCallParts, textContent) { ParticipantName = message.From };
+
+        // Don't set participant name for assistant when it is tool call
+        // fix https://github.com/microsoft/autogen/issues/3437
+        var chatRequestMessage = new AssistantChatMessage(toolCallParts, textContent);
 
         return [chatRequestMessage];
     }
diff --git a/dotnet/test/AutoGen.OpenAI.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt b/dotnet/test/AutoGen.OpenAI.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
index 3574e593d..55bd6502b 100644
--- a/dotnet/test/AutoGen.OpenAI.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
+++ b/dotnet/test/AutoGen.OpenAI.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
@@ -139,7 +139,7 @@
       {
         "Role": "assistant",
         "Content": [],
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
@@ -184,7 +184,7 @@
       {
         "Role": "assistant",
         "Content": [],
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
@@ -210,7 +210,7 @@
       {
         "Role": "assistant",
         "Content": [],
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
diff --git a/dotnet/test/AutoGen.OpenAI.Tests/OpenAIChatAgentTest.cs b/dotnet/test/AutoGen.OpenAI.Tests/OpenAIChatAgentTest.cs
index 04f4d3d4d..992bf9b60 100644
--- a/dotnet/test/AutoGen.OpenAI.Tests/OpenAIChatAgentTest.cs
+++ b/dotnet/test/AutoGen.OpenAI.Tests/OpenAIChatAgentTest.cs
@@ -27,6 +27,12 @@ public partial class OpenAIChatAgentTest
         return $"The weather in {location} is sunny.";
     }
 
+    [Function]
+    public async Task<string> CalculateTaxAsync(string location, double income)
+    {
+        return $"[CalculateTax] The tax in {location} for income {income} is 1000.";
+    }
+
     [ApiKeyFact("AZURE_OPENAI_API_KEY", "AZURE_OPENAI_ENDPOINT", "AZURE_OPENAI_DEPLOY_NAME")]
     public async Task BasicConversationTestAsync()
     {
@@ -246,6 +252,65 @@ public partial class OpenAIChatAgentTest
         respond.GetContent()?.Should().NotBeNullOrEmpty();
     }
 
+
+    [ApiKeyFact("AZURE_OPENAI_API_KEY", "AZURE_OPENAI_ENDPOINT", "AZURE_OPENAI_DEPLOY_NAME")]
+    public async Task ItProduceValidContentAfterFunctionCall()
+    {
+        // https://github.com/microsoft/autogen/issues/3437
+        var deployName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOY_NAME") ?? throw new Exception("Please set AZURE_OPENAI_DEPLOY_NAME environment variable.");
+        var openaiClient = CreateOpenAIClientFromAzureOpenAI();
+        var options = new ChatCompletionOptions()
+        {
+            Temperature = 0.7f,
+            MaxTokens = 1,
+        };
+
+        var agentName = "assistant";
+
+        var getWeatherToolCall = new ToolCall(this.GetWeatherAsyncFunctionContract.Name, "{\"location\":\"Seattle\"}");
+        var getWeatherToolCallResult = new ToolCall(this.GetWeatherAsyncFunctionContract.Name, "{\"location\":\"Seattle\"}", "The weather in Seattle is sunny.");
+        var getWeatherToolCallMessage = new ToolCallMessage([getWeatherToolCall], from: agentName);
+        var getWeatherToolCallResultMessage = new ToolCallResultMessage([getWeatherToolCallResult], from: agentName);
+        var getWeatherAggregateMessage = new ToolCallAggregateMessage(getWeatherToolCallMessage, getWeatherToolCallResultMessage, from: agentName);
+
+        var calculateTaxToolCall = new ToolCall(this.CalculateTaxAsyncFunctionContract.Name, "{\"location\":\"Seattle\",\"income\":1000}");
+        var calculateTaxToolCallResult = new ToolCall(this.CalculateTaxAsyncFunctionContract.Name, "{\"location\":\"Seattle\",\"income\":1000}", "The tax in Seattle for income 1000 is 1000.");
+        var calculateTaxToolCallMessage = new ToolCallMessage([calculateTaxToolCall], from: agentName);
+        var calculateTaxToolCallResultMessage = new ToolCallResultMessage([calculateTaxToolCallResult], from: agentName);
+        var calculateTaxAggregateMessage = new ToolCallAggregateMessage(calculateTaxToolCallMessage, calculateTaxToolCallResultMessage, from: agentName);
+
+        var chatHistory = new List<IMessage>()
+        {
+            new TextMessage(Role.User, "What's the weather in Seattle", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in Seattle is sunny, now check the tax in seattle", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in Paris", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in Paris is sunny, now check the tax in Paris", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in New York", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in New York is sunny, now check the tax in New York", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in London", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in London is sunny, now check the tax in London", from: "admin"),
+        };
+
+        var agent = new OpenAIChatAgent(
+            chatClient: openaiClient.GetChatClient(deployName),
+            name: "assistant",
+            options: options)
+            .RegisterMessageConnector();
+
+        var res = await agent.GenerateReplyAsync(chatHistory, new GenerateReplyOptions
+        {
+            MaxToken = 1024,
+            Functions = [this.GetWeatherAsyncFunctionContract, this.CalculateTaxAsyncFunctionContract],
+        });
+    }
+
     private OpenAIClient CreateOpenAIClientFromAzureOpenAI()
     {
         var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? throw new Exception("Please set AZURE_OPENAI_ENDPOINT environment variable.");
diff --git a/dotnet/test/AutoGen.OpenAI.Tests/OpenAIMessageTests.cs b/dotnet/test/AutoGen.OpenAI.Tests/OpenAIMessageTests.cs
index a05f440a1..3a2048c2f 100644
--- a/dotnet/test/AutoGen.OpenAI.Tests/OpenAIMessageTests.cs
+++ b/dotnet/test/AutoGen.OpenAI.Tests/OpenAIMessageTests.cs
@@ -276,7 +276,10 @@ public class OpenAIMessageTests
                 var innerMessage = msgs.Last();
                 innerMessage!.Should().BeOfType<MessageEnvelope<ChatMessage>>();
                 var chatRequestMessage = (AssistantChatMessage)((MessageEnvelope<ChatMessage>)innerMessage!).Content;
-                chatRequestMessage.ParticipantName.Should().Be("assistant");
+                // when the message is a tool call message
+                // the name field should not be set
+                // please visit OpenAIChatRequestMessageConnector class for more information
+                chatRequestMessage.ParticipantName.Should().BeNullOrEmpty();
                 chatRequestMessage.ToolCalls.Count().Should().Be(1);
                 chatRequestMessage.Content.First().Text.Should().Be("textContent");
                 chatRequestMessage.ToolCalls.First().Should().BeOfType<ChatToolCall>();
@@ -307,7 +310,10 @@ public class OpenAIMessageTests
                 innerMessage!.Should().BeOfType<MessageEnvelope<ChatMessage>>();
                 var chatRequestMessage = (AssistantChatMessage)((MessageEnvelope<ChatMessage>)innerMessage!).Content;
                 chatRequestMessage.Content.Should().BeNullOrEmpty();
-                chatRequestMessage.ParticipantName.Should().Be("assistant");
+                // when the message is a tool call message
+                // the name field should not be set
+                // please visit OpenAIChatRequestMessageConnector class for more information
+                chatRequestMessage.ParticipantName.Should().BeNullOrEmpty();
                 chatRequestMessage.ToolCalls.Count().Should().Be(2);
                 for (int i = 0; i < chatRequestMessage.ToolCalls.Count(); i++)
                 {
diff --git a/dotnet/test/AutoGen.OpenAI.V1.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt b/dotnet/test/AutoGen.OpenAI.V1.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
index e8e9af84d..877bc57bf 100644
--- a/dotnet/test/AutoGen.OpenAI.V1.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
+++ b/dotnet/test/AutoGen.OpenAI.V1.Tests/ApprovalTests/OpenAIMessageTests.BasicMessageTest.approved.txt
@@ -81,7 +81,7 @@
       {
         "Role": "assistant",
         "Content": "",
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
@@ -126,7 +126,7 @@
       {
         "Role": "assistant",
         "Content": "",
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
@@ -152,7 +152,7 @@
       {
         "Role": "assistant",
         "Content": "",
-        "Name": "assistant",
+        "Name": null,
         "TooCall": [
           {
             "Type": "Function",
diff --git a/dotnet/test/AutoGen.OpenAI.V1.Tests/MathClassTest.cs b/dotnet/test/AutoGen.OpenAI.V1.Tests/MathClassTest.cs
index a1f9541f4..d6055fb78 100644
--- a/dotnet/test/AutoGen.OpenAI.V1.Tests/MathClassTest.cs
+++ b/dotnet/test/AutoGen.OpenAI.V1.Tests/MathClassTest.cs
@@ -4,6 +4,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.Json;
 using System.Threading;
 using System.Threading.Tasks;
 using AutoGen.OpenAI.V1.Extension;
@@ -45,7 +46,11 @@ namespace AutoGen.OpenAI.V1.Tests
                 _output.WriteLine($"agent name: {agent.Name}");
                 foreach (var message in messages)
                 {
-                    _output.WriteLine(message.FormatMessage());
+                    if (message is IMessage<object> envelope)
+                    {
+                        var json = JsonSerializer.Serialize(envelope.Content, new JsonSerializerOptions { WriteIndented = true });
+                        _output.WriteLine(json);
+                    }
                 }
 
                 throw;
@@ -149,9 +154,9 @@ You create math question and ask student to answer it.
 Then you check if the answer is correct.
 If the answer is wrong, you ask student to fix it",
                 modelName: model)
-                .RegisterMessageConnector()
-                .RegisterStreamingMiddleware(functionCallMiddleware)
-                .RegisterMiddleware(Print);
+                .RegisterMiddleware(Print)
+                .RegisterMiddleware(new OpenAIChatRequestMessageConnector())
+                .RegisterMiddleware(functionCallMiddleware);
 
             return teacher;
         }
diff --git a/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIChatAgentTest.cs b/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIChatAgentTest.cs
index 0957cc9f4..1000339c6 100644
--- a/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIChatAgentTest.cs
+++ b/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIChatAgentTest.cs
@@ -22,7 +22,13 @@ public partial class OpenAIChatAgentTest
     [Function]
     public async Task<string> GetWeatherAsync(string location)
     {
-        return $"The weather in {location} is sunny.";
+        return $"[GetWeather] The weather in {location} is sunny.";
+    }
+
+    [Function]
+    public async Task<string> CalculateTaxAsync(string location, double income)
+    {
+        return $"[CalculateTax] The tax in {location} for income {income} is 1000.";
     }
 
     [ApiKeyFact("AZURE_OPENAI_API_KEY", "AZURE_OPENAI_ENDPOINT", "AZURE_OPENAI_DEPLOY_NAME")]
@@ -270,6 +276,64 @@ public partial class OpenAIChatAgentTest
         action.Should().ThrowExactly<ArgumentException>().WithMessage("Messages should not be provided in options");
     }
 
+    [ApiKeyFact("AZURE_OPENAI_API_KEY", "AZURE_OPENAI_ENDPOINT", "AZURE_OPENAI_DEPLOY_NAME")]
+    public async Task ItProduceValidContentAfterFunctionCall()
+    {
+        // https://github.com/microsoft/autogen/issues/3437
+        var deployName = Environment.GetEnvironmentVariable("AZURE_OPENAI_DEPLOY_NAME") ?? throw new Exception("Please set AZURE_OPENAI_DEPLOY_NAME environment variable.");
+        var openaiClient = CreateOpenAIClientFromAzureOpenAI();
+        var options = new ChatCompletionsOptions(deployName, [])
+        {
+            Temperature = 0.7f,
+            MaxTokens = 1,
+        };
+
+        var agentName = "assistant";
+
+        var getWeatherToolCall = new ToolCall(this.GetWeatherAsyncFunctionContract.Name, "{\"location\":\"Seattle\"}");
+        var getWeatherToolCallResult = new ToolCall(this.GetWeatherAsyncFunctionContract.Name, "{\"location\":\"Seattle\"}", "The weather in Seattle is sunny.");
+        var getWeatherToolCallMessage = new ToolCallMessage([getWeatherToolCall], from: agentName);
+        var getWeatherToolCallResultMessage = new ToolCallResultMessage([getWeatherToolCallResult], from: agentName);
+        var getWeatherAggregateMessage = new ToolCallAggregateMessage(getWeatherToolCallMessage, getWeatherToolCallResultMessage, from: agentName);
+
+        var calculateTaxToolCall = new ToolCall(this.CalculateTaxAsyncFunctionContract.Name, "{\"location\":\"Seattle\",\"income\":1000}");
+        var calculateTaxToolCallResult = new ToolCall(this.CalculateTaxAsyncFunctionContract.Name, "{\"location\":\"Seattle\",\"income\":1000}", "The tax in Seattle for income 1000 is 1000.");
+        var calculateTaxToolCallMessage = new ToolCallMessage([calculateTaxToolCall], from: agentName);
+        var calculateTaxToolCallResultMessage = new ToolCallResultMessage([calculateTaxToolCallResult], from: agentName);
+        var calculateTaxAggregateMessage = new ToolCallAggregateMessage(calculateTaxToolCallMessage, calculateTaxToolCallResultMessage, from: agentName);
+
+        var chatHistory = new List<IMessage>()
+        {
+            new TextMessage(Role.User, "What's the weather in Seattle", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in Seattle is sunny, now check the tax in seattle", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in Paris", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in Paris is sunny, now check the tax in Paris", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in New York", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in New York is sunny, now check the tax in New York", from: "admin"),
+            calculateTaxAggregateMessage,
+            new TextMessage(Role.User, "what's the weather in London", from: "user"),
+            getWeatherAggregateMessage,
+            new TextMessage(Role.User, "The weather in London is sunny, now check the tax in London", from: "admin"),
+        };
+
+        var agent = new OpenAIChatAgent(
+            openAIClient: openaiClient,
+            name: "assistant",
+            options: options)
+            .RegisterMessageConnector();
+
+        var res = await agent.GenerateReplyAsync(chatHistory, new GenerateReplyOptions
+        {
+            MaxToken = 1024,
+            Functions = [this.GetWeatherAsyncFunctionContract, this.CalculateTaxAsyncFunctionContract],
+        });
+    }
+
     private OpenAIClient CreateOpenAIClientFromAzureOpenAI()
     {
         var endpoint = Environment.GetEnvironmentVariable("AZURE_OPENAI_ENDPOINT") ?? throw new Exception("Please set AZURE_OPENAI_ENDPOINT environment variable.");
diff --git a/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIMessageTests.cs b/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIMessageTests.cs
index 3050c4e8e..876416fdc 100644
--- a/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIMessageTests.cs
+++ b/dotnet/test/AutoGen.OpenAI.V1.Tests/OpenAIMessageTests.cs
@@ -278,7 +278,10 @@ public class OpenAIMessageTests
                 var innerMessage = msgs.Last();
                 innerMessage!.Should().BeOfType<MessageEnvelope<ChatRequestMessage>>();
                 var chatRequestMessage = (ChatRequestAssistantMessage)((MessageEnvelope<ChatRequestMessage>)innerMessage!).Content;
-                chatRequestMessage.Name.Should().Be("assistant");
+                // when the message is a tool call message
+                // the name field should not be set
+                // please visit OpenAIChatRequestMessageConnector class for more information
+                chatRequestMessage.Name.Should().BeNullOrEmpty();
                 chatRequestMessage.ToolCalls.Count().Should().Be(1);
                 chatRequestMessage.Content.Should().Be("textContent");
                 chatRequestMessage.ToolCalls.First().Should().BeOfType<ChatCompletionsFunctionToolCall>();
@@ -309,7 +312,11 @@ public class OpenAIMessageTests
                 innerMessage!.Should().BeOfType<MessageEnvelope<ChatRequestMessage>>();
                 var chatRequestMessage = (ChatRequestAssistantMessage)((MessageEnvelope<ChatRequestMessage>)innerMessage!).Content;
                 chatRequestMessage.Content.Should().BeNullOrEmpty();
-                chatRequestMessage.Name.Should().Be("assistant");
+
+                // when the message is a tool call message
+                // the name field should not be set
+                // please visit OpenAIChatRequestMessageConnector class for more information
+                chatRequestMessage.Name.Should().BeNullOrEmpty();
                 chatRequestMessage.ToolCalls.Count().Should().Be(2);
                 for (int i = 0; i < chatRequestMessage.ToolCalls.Count(); i++)
                 {