.NET: add workflow agent tool call message filtering

dotnet/src/Microsoft.Agents.AI.Workflows/Futures.cs

@@ -26,7 +26,7 @@ public static class Futures
     /// <c>[Obsolete]</c> in v2.0.0 when the new behavior becomes default, and removed in v3.0.0.
     /// </para>
     /// <para>
-    /// <b>Interaction with <see cref="WorkflowHostingExtensions.AsAIAgent"/>.</b> When this flag
+    /// <b>Interaction with <see cref="WorkflowHostingExtensions.AsAIAgent(Workflow, string?, string?, string?, IWorkflowExecutionEnvironment?, bool, bool)"/>.</b> When this flag
     /// is <see langword="true"/>, <see cref="AgentResponseEvent"/> joins
     /// <see cref="AgentResponseUpdateEvent"/> in being forwarded out of the agent surface
     /// unconditionally — neither honors the host's <c>includeWorkflowOutputsInResponse</c>

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowHostAgent.cs

@@ -20,11 +20,12 @@ internal sealed class WorkflowHostAgent : AIAgent
     private readonly IWorkflowExecutionEnvironment _executionEnvironment;
     private readonly bool _includeExceptionDetails;
     private readonly bool _includeWorkflowOutputsInResponse;
+    private readonly bool _filterToolCallMessages;
     private readonly Task<ProtocolDescriptor> _describeTask;
 
     private readonly ConcurrentDictionary<string, string> _assignedSessionIds = [];
 
-    public WorkflowHostAgent(Workflow workflow, string? id = null, string? name = null, string? description = null, IWorkflowExecutionEnvironment? executionEnvironment = null, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false)
+    public WorkflowHostAgent(Workflow workflow, string? id = null, string? name = null, string? description = null, IWorkflowExecutionEnvironment? executionEnvironment = null, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false, bool filterToolCallMessages = false)
     {
         this._workflow = Throw.IfNull(workflow);
 
@@ -42,6 +43,7 @@ public WorkflowHostAgent(Workflow workflow, string? id = null, string? name = nu
 
         this._includeExceptionDetails = includeExceptionDetails;
         this._includeWorkflowOutputsInResponse = includeWorkflowOutputsInResponse;
+        this._filterToolCallMessages = filterToolCallMessages;
 
         this._id = id;
         this.Name = name;
@@ -74,7 +76,7 @@ private async ValueTask ValidateWorkflowAsync()
     }
 
     protected override ValueTask<AgentSession> CreateSessionCoreAsync(CancellationToken cancellationToken = default)
-        => new(new WorkflowSession(this._workflow, this.GenerateNewId(), this._executionEnvironment, this._includeExceptionDetails, this._includeWorkflowOutputsInResponse));
+        => new(new WorkflowSession(this._workflow, this.GenerateNewId(), this._executionEnvironment, this._includeExceptionDetails, this._includeWorkflowOutputsInResponse, this._filterToolCallMessages));
 
     protected override ValueTask<JsonElement> SerializeSessionCoreAsync(AgentSession session, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
     {
@@ -89,7 +91,7 @@ protected override ValueTask<JsonElement> SerializeSessionCoreAsync(AgentSession
     }
 
     protected override ValueTask<AgentSession> DeserializeSessionCoreAsync(JsonElement serializedState, JsonSerializerOptions? jsonSerializerOptions = null, CancellationToken cancellationToken = default)
-        => new(new WorkflowSession(this._workflow, serializedState, this._executionEnvironment, this._includeExceptionDetails, this._includeWorkflowOutputsInResponse, jsonSerializerOptions));
+        => new(new WorkflowSession(this._workflow, serializedState, this._executionEnvironment, this._includeExceptionDetails, this._includeWorkflowOutputsInResponse, this._filterToolCallMessages, jsonSerializerOptions));
 
     private async ValueTask<WorkflowSession> UpdateSessionAsync(IEnumerable<ChatMessage> messages, AgentSession? session = null, CancellationToken cancellationToken = default)
     {

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowHostingExtensions.cs

@@ -37,6 +37,36 @@ public static AIAgent AsAIAgent(
         return new WorkflowHostAgent(workflow, id, name, description, executionEnvironment, includeExceptionDetails, includeWorkflowOutputsInResponse);
     }
 
+    /// <summary>
+    /// Convert a workflow with the appropriate primary input type to an <see cref="AIAgent"/>.
+    /// </summary>
+    /// <param name="workflow">The workflow to be hosted by the resulting <see cref="AIAgent"/></param>
+    /// <param name="filterToolCallMessages">If <see langword="true"/>, will remove <see cref="FunctionCallContent"/> and
+    /// <see cref="FunctionResultContent"/> from messages surfaced by the hosted workflow agent.</param>
+    /// <param name="id">A unique id for the hosting <see cref="AIAgent"/>.</param>
+    /// <param name="name">A name for the hosting <see cref="AIAgent"/>.</param>
+    /// <param name="description">A description for the hosting <see cref="AIAgent"/>.</param>
+    /// <param name="executionEnvironment">Specify the execution environment to use when running the workflows. See
+    /// <see cref="InProcessExecution.OffThread"/>, <see cref="InProcessExecution.Concurrent"/> and
+    /// <see cref="InProcessExecution.Lockstep"/> for the in-process environments.</param>
+    /// <param name="includeExceptionDetails">If <see langword="true"/>, will include <see cref="System.Exception.Message"/>
+    /// in the <see cref="ErrorContent"/> representing the workflow error.</param>
+    /// <param name="includeWorkflowOutputsInResponse">If <see langword="true"/>, will transform outgoing workflow outputs
+    /// into content in <see cref="AgentResponseUpdate"/>s or the <see cref="AgentResponse"/> as appropriate.</param>
+    /// <returns></returns>
+    public static AIAgent AsAIAgent(
+        this Workflow workflow,
+        bool filterToolCallMessages,
+        string? id = null,
+        string? name = null,
+        string? description = null,
+        IWorkflowExecutionEnvironment? executionEnvironment = null,
+        bool includeExceptionDetails = false,
+        bool includeWorkflowOutputsInResponse = false)
+    {
+        return new WorkflowHostAgent(workflow, id, name, description, executionEnvironment, includeExceptionDetails, includeWorkflowOutputsInResponse, filterToolCallMessages);
+    }
+
     internal static FunctionCallContent ToFunctionCall(this ExternalRequest request)
     {
         Dictionary<string, object?> parameters = new()

dotnet/src/Microsoft.Agents.AI.Workflows/WorkflowSession.cs

@@ -30,6 +30,7 @@ internal sealed class WorkflowSession : AgentSession
 
     private readonly bool _includeExceptionDetails;
     private readonly bool _includeWorkflowOutputsInResponse;
+    private readonly bool _filterToolCallMessages;
 
     private InMemoryCheckpointManager? _inMemoryCheckpointManager;
 
@@ -68,11 +69,12 @@ internal static bool VerifyCheckpointingConfiguration(IWorkflowExecutionEnvironm
         return true;
     }
 
-    public WorkflowSession(Workflow workflow, string sessionId, IWorkflowExecutionEnvironment executionEnvironment, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false)
+    public WorkflowSession(Workflow workflow, string sessionId, IWorkflowExecutionEnvironment executionEnvironment, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false, bool filterToolCallMessages = false)
     {
         this._workflow = Throw.IfNull(workflow);
         this._includeExceptionDetails = includeExceptionDetails;
         this._includeWorkflowOutputsInResponse = includeWorkflowOutputsInResponse;
+        this._filterToolCallMessages = filterToolCallMessages;
 
         IWorkflowExecutionEnvironment env = Throw.IfNull(executionEnvironment);
         if (VerifyCheckpointingConfiguration(env, out InProcessExecutionEnvironment? inProcEnv))
@@ -96,11 +98,12 @@ private CheckpointManager EnsureExternalizedInMemoryCheckpointing()
         return new(this._inMemoryCheckpointManager ??= new());
     }
 
-    public WorkflowSession(Workflow workflow, JsonElement serializedSession, IWorkflowExecutionEnvironment executionEnvironment, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false, JsonSerializerOptions? jsonSerializerOptions = null)
+    public WorkflowSession(Workflow workflow, JsonElement serializedSession, IWorkflowExecutionEnvironment executionEnvironment, bool includeExceptionDetails = false, bool includeWorkflowOutputsInResponse = false, bool filterToolCallMessages = false, JsonSerializerOptions? jsonSerializerOptions = null)
     {
         this._workflow = Throw.IfNull(workflow);
         this._includeExceptionDetails = includeExceptionDetails;
         this._includeWorkflowOutputsInResponse = includeWorkflowOutputsInResponse;
+        this._filterToolCallMessages = filterToolCallMessages;
 
         IWorkflowExecutionEnvironment env = Throw.IfNull(executionEnvironment);
 
@@ -173,6 +176,71 @@ public AgentResponseUpdate CreateUpdate(string responseId, object raw, ChatMessa
         };
     }
 
+    private AgentResponseUpdate? FilterToolCallContents(AgentResponseUpdate update)
+    {
+        if (!this._filterToolCallMessages || !ContainsToolCallContent(update.Contents))
+        {
+            return update;
+        }
+
+        List<AIContent> retainedContents = update.Contents
+            .Where(static content => !IsToolCallContent(content))
+            .ToList();
+
+        if (retainedContents.Count == 0)
+        {
+            return null;
+        }
+
+        return new AgentResponseUpdate
+        {
+            AdditionalProperties = update.AdditionalProperties,
+            AgentId = update.AgentId,
+            AuthorName = update.AuthorName,
+            Contents = retainedContents,
+            ContinuationToken = update.ContinuationToken,
+            CreatedAt = update.CreatedAt,
+            FinishReason = update.FinishReason,
+            MessageId = update.MessageId,
+            RawRepresentation = update.RawRepresentation,
+            ResponseId = update.ResponseId,
+            Role = update.Role,
+        };
+    }
+
+    private ChatMessage? FilterToolCallContents(ChatMessage message)
+    {
+        if (!this._filterToolCallMessages || !ContainsToolCallContent(message.Contents))
+        {
+            return message;
+        }
+
+        List<AIContent> retainedContents = message.Contents
+            .Where(static content => !IsToolCallContent(content))
+            .ToList();
+
+        if (retainedContents.Count == 0)
+        {
+            return null;
+        }
+
+        ChatMessage filteredMessage = message.Clone();
+        filteredMessage.Contents = retainedContents;
+        return filteredMessage;
+    }
+
+    private AgentResponseUpdate? CreateFilteredUpdate(string responseId, object raw, ChatMessage message)
+    {
+        ChatMessage? filteredMessage = this.FilterToolCallContents(message);
+        return filteredMessage == null ? null : this.CreateUpdate(responseId, raw, filteredMessage);
+    }
+
+    private static bool ContainsToolCallContent(IEnumerable<AIContent> contents)
+        => contents.Any(static content => IsToolCallContent(content));
+
+    private static bool IsToolCallContent(AIContent content)
+        => content is FunctionCallContent or FunctionResultContent;
+
     private async ValueTask<ResumeRunResult> CreateOrResumeRunAsync(List<ChatMessage> messages, CancellationToken cancellationToken = default)
     {
         // The workflow is validated to be a ChatProtocol workflow by the WorkflowHostAgent before creating the session,
@@ -480,7 +548,11 @@ IAsyncEnumerable<AgentResponseUpdate> InvokeStageAsync(
             switch (evt)
             {
                 case AgentResponseUpdateEvent agentUpdate:
-                    yield return agentUpdate.Update;
+                    AgentResponseUpdate? filteredUpdate = this.FilterToolCallContents(agentUpdate.Update);
+                    if (filteredUpdate != null)
+                    {
+                        yield return filteredUpdate;
+                    }
                     break;
 
                 case RequestInfoEvent requestInfo:
@@ -553,7 +625,11 @@ IAsyncEnumerable<AgentResponseUpdate> InvokeStageAsync(
                     // as an output executor.
                     foreach (ChatMessage message in agentResponse.Response.Messages)
                     {
-                        yield return this.CreateUpdate(this.LastResponseId, evt, message);
+                        AgentResponseUpdate? filteredMessageUpdate = this.CreateFilteredUpdate(this.LastResponseId, evt, message);
+                        if (filteredMessageUpdate != null)
+                        {
+                            yield return filteredMessageUpdate;
+                        }
                     }
                     break;
 
@@ -576,7 +652,11 @@ IAsyncEnumerable<AgentResponseUpdate> InvokeStageAsync(
 
                     foreach (ChatMessage message in updateMessages)
                     {
-                        yield return this.CreateUpdate(this.LastResponseId, evt, message);
+                        AgentResponseUpdate? filteredMessageUpdate = this.CreateFilteredUpdate(this.LastResponseId, evt, message);
+                        if (filteredMessageUpdate != null)
+                        {
+                            yield return filteredMessageUpdate;
+                        }
                     }
                     break;
 

dotnet/tests/Microsoft.Agents.AI.Workflows.UnitTests/WorkflowHostSmokeTests.cs

@@ -216,6 +216,9 @@ public override ValueTask HandleAsync(string message, IWorkflowContext context,
 
 public class WorkflowHostSmokeTests : AIAgentHostingExecutorTestsBase
 {
+    private const string ToolCallText = "Before tool call.";
+    private const string FinalText = "Final answer.";
+
     private sealed class AlwaysFailsAIAgent(bool failByThrowing) : AIAgent
     {
         private sealed class Session : AgentSession
@@ -263,6 +266,38 @@ private static Workflow CreateWorkflow(bool failByThrowing)
         return new WorkflowBuilder(agent).Build();
     }
 
+    private static Workflow CreateToolCallWorkflow()
+    {
+        List<ChatMessage> messages =
+        [
+            new(ChatRole.Assistant,
+            [
+                new TextContent(ToolCallText),
+                new FunctionCallContent("call_1", "get_data"),
+            ])
+            {
+                MessageId = "tool-call-message",
+            },
+            new(ChatRole.Tool, [new FunctionResultContent("call_1", "tool result")])
+            {
+                MessageId = "tool-result-message",
+            },
+            new(ChatRole.Assistant, [new TextContent(FinalText)])
+            {
+                MessageId = "final-message",
+            },
+        ];
+
+        TestReplayAgent agent = new(messages, TestAgentId, TestAgentName);
+        ExecutorBinding binding = agent.BindAsExecutor(new AIAgentHostOptions
+        {
+            EmitAgentUpdateEvents = true,
+            EmitAgentResponseEvents = true,
+        });
+
+        return new WorkflowBuilder(binding).Build();
+    }
+
     [Theory]
     [InlineData(true, true)]
     [InlineData(true, false)]
@@ -299,6 +334,53 @@ public async Task Test_AsAgent_ErrorContentStreamedOutAsync(bool includeExceptio
         hadErrorContent.Should().BeTrue();
     }
 
+    [Fact]
+    public async Task Test_AsAgent_DefaultPreservesToolCallMessagesAsync()
+    {
+        // Arrange
+        Workflow workflow = CreateToolCallWorkflow();
+        AIAgent workflowAgent = workflow.AsAIAgent("WorkflowAgent");
+
+        // Act
+        AgentResponse response = await workflowAgent.RunAsync(new ChatMessage(ChatRole.User, "Hello"));
+
+        // Assert
+        List<AIContent> contents = [.. response.Messages.SelectMany(message => message.Contents)];
+        contents.Should().Contain(content => content is FunctionCallContent);
+        contents.Should().Contain(content => content is FunctionResultContent);
+    }
+
+    [Theory]
+    [InlineData(false)]
+    [InlineData(true)]
+    public async Task Test_AsAgent_FilterToolCallMessagesRemovesToolCallContentsAsync(bool runStreaming)
+    {
+        // Arrange
+        Workflow workflow = CreateToolCallWorkflow();
+        AIAgent workflowAgent = workflow.AsAIAgent(filterToolCallMessages: true, id: "WorkflowAgent");
+
+        // Act
+        List<AIContent> contents;
+        if (runStreaming)
+        {
+            List<AgentResponseUpdate> updates = await workflowAgent.RunStreamingAsync(new ChatMessage(ChatRole.User, "Hello")).ToListAsync();
+            contents = [.. updates.SelectMany(update => update.Contents)];
+        }
+        else
+        {
+            AgentResponse response = await workflowAgent.RunAsync(new ChatMessage(ChatRole.User, "Hello"));
+            contents = [.. response.Messages.SelectMany(message => message.Contents)];
+        }
+
+        // Assert
+        contents.Should().NotContain(content => content is FunctionCallContent);
+        contents.Should().NotContain(content => content is FunctionResultContent);
+
+        List<string> textContents = [.. contents.OfType<TextContent>().Select(content => content.Text)];
+        textContents.Should().Contain(ToolCallText);
+        textContents.Should().Contain(FinalText);
+    }
+
     /// <summary>
     /// Tests that when a workflow emits a RequestInfoEvent with FunctionCallContent data,
     /// the AgentResponseUpdate preserves the original FunctionCallContent type.