.NET: [Bug]: Durable Agent fails to serialize state when using MCP tools

[shibayan]

Description

When configured to use MCP with Durable Agent, a JSON serializer exception occurs during Agent execution, preventing normal operation. Tool invocations using local methods instead of MCP function correctly.

Code Sample

var mcpClient = await McpClient.CreateAsync(new HttpClientTransport(new HttpClientTransportOptions
{
    Endpoint = new Uri("https://***.azurewebsites.net/runtime/webhooks/mcp")
}));

var tools = await mcpClient.ListToolsAsync();

var refineAgent = chatClient.CreateAIAgent(
    instructions: "Please rewrite the entered text into polished language suitable for a press release.",
    name: "RefineAgent",
    tools: tools.Cast<AITool>().ToArray()
);



var refineAgent = context.GetAgent("RefineAgent");

var refineResponse = await refineAgent.RunAsync<TextResponse>(topic);

Error Messages / Stack Traces

Unhandled exception in entity operation @dafx-refineagent@b1a3b89ce591535e9c1b7573697dca4d/Run.
Result: Unhandled exception in entity operation @dafx-refineagent@b1a3b89ce591535e9c1b7573697dca4d/Run.
Type:
Exception: System.NotSupportedException: JsonTypeInfo metadata for type 'Microsoft.Extensions.AI.TextContent' was not provided by TypeInfoResolver of type 'Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext'. If using source generation, ensure that all root types passed to the serializer have been annotated with 'JsonSerializableAttribute', along with any types that might be serialized polymorphically. The unsupported member type is located on type 'System.Object'. Path: $.Result.
 ---> System.NotSupportedException: JsonTypeInfo metadata for type 'Microsoft.Extensions.AI.TextContent' was not provided by TypeInfoResolver of type 'Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext'. If using source generation, ensure that all root types passed to the serializer have been annotated with 'JsonSerializableAttribute', along with any types that might be serialized polymorphically.
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException_NoMetadataForType(Type type, IJsonTypeInfoResolver resolver)
   at System.Text.Json.JsonSerializerOptions.GetTypeInfoInternal(Type type, Boolean ensureConfigured, Nullable`1 ensureNotNull, Boolean resolveIfMutable, Boolean fallBackToNearestAncestorType)
   at System.Text.Json.WriteStackFrame.InitializePolymorphicReEntry(Type runtimeType, JsonSerializerOptions options)
   at System.Text.Json.Serialization.JsonConverter.ResolvePolymorphicConverter(Object value, JsonTypeInfo jsonTypeInfo, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   --- End of inner exception stack trace ---
   at System.Text.Json.ThrowHelper.ThrowNotSupportedException(WriteStack& state, Exception innerException)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IReadOnlyListDurableAgentStateContentSerializeHandler(Utf8JsonWriter writer, IReadOnlyList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IReadOnlyListDurableAgentStateMessageSerializeHandler(Utf8JsonWriter writer, IReadOnlyList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IListDurableAgentStateEntrySerializeHandler(Utf8JsonWriter writer, IList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonConverter.Write(Utf8JsonWriter writer, DurableAgentState value, JsonSerializerOptions options)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.SerializeAsObject(Utf8JsonWriter writer, Object rootValue)
   at System.Text.Json.JsonSerializer.WriteBytesAsObject(Object value, JsonTypeInfo jsonTypeInfo)
   at Azure.Core.Serialization.JsonObjectSerializer.SerializeToBinaryDataInternal(Object value, Type inputType)
   at Azure.Core.Serialization.JsonObjectSerializer.Serialize(Object value, Type inputType, CancellationToken cancellationToken)
   at Microsoft.Azure.Functions.Worker.Extensions.DurableTask.ObjectConverterShim.Serialize(Object value) in /_/src/Worker.Extensions.DurableTask/ObjectConverterShim.cs:line 42
   at Microsoft.DurableTask.Worker.Shims.TaskEntityShim.StateShim.SetState(Object state)
   at Microsoft.DurableTask.Entities.TaskEntityHelpers.UnwrapTask(TaskEntityState state, Func`1 callback, Task task, Type declared)
   at Microsoft.DurableTask.Worker.Shims.TaskEntityShim.ExecuteOperationBatchAsync(EntityBatchRequest operations)
on.ThrowHelper.ThrowNotSupportedException(WriteStack& state, Exception innerException)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IReadOnlyListDurableAgentStateContentSerializeHandler(Utf8JsonWriter writer, IReadOnlyList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IReadOnlyListDurableAgentStateMessageSerializeHandler(Utf8JsonWriter writer, IReadOnlyList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWriteAsObject(Utf8JsonWriter writer, Object value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonContext.IListDurableAgentStateEntrySerializeHandler(Utf8JsonWriter writer, IList`1 value)
   at System.Text.Json.Serialization.Converters.JsonMetadataServicesConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.GetMemberAndWriteJson(Object obj, WriteStack& state, Utf8JsonWriter writer)
   at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryWrite(Utf8JsonWriter writer, T value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.JsonSerializer.Serialize[TValue](Utf8JsonWriter writer, TValue value, JsonTypeInfo`1 jsonTypeInfo)
   at Microsoft.Agents.AI.DurableTask.State.DurableAgentStateJsonConverter.Write(Utf8JsonWriter writer, DurableAgentState value, JsonSerializerOptions options)
   at System.Text.Json.Serialization.JsonConverter`1.TryWrite(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.JsonConverter`1.WriteCore(Utf8JsonWriter writer, T& value, JsonSerializerOptions options, WriteStack& state)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.Serialize(Utf8JsonWriter writer, T& rootValue, Object rootValueBoxed)
   at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.SerializeAsObject(Utf8JsonWriter writer, Object rootValue)
   at System.Text.Json.JsonSerializer.WriteBytesAsObject(Object value, JsonTypeInfo jsonTypeInfo)
   at Azure.Core.Serialization.JsonObjectSerializer.SerializeToBinaryDataInternal(Object value, Type inputType)
   at Azure.Core.Serialization.JsonObjectSerializer.Serialize(Object value, Type inputType, CancellationToken cancellationToken)
   at Microsoft.Azure.Functions.Worker.Extensions.DurableTask.ObjectConverterShim.Serialize(Object value) in /_/src/Worker.Extensions.DurableTask/ObjectConverterShim.cs:line 42
   at Microsoft.DurableTask.Worker.Shims.TaskEntityShim.StateShim.SetState(Object state)
   at Microsoft.DurableTask.Entities.TaskEntityHelpers.UnwrapTask(TaskEntityState state, Func`1 callback, Task task, Type declared)
   at Microsoft.DurableTask.Worker.Shims.TaskEntityShim.ExecuteOperationBatchAsync(EntityBatchRequest operations).

Package Versions

Microsoft.Agents.AI.Hosting.AzureFunctions: 1.0.0-preview.260108.1, Microsoft.Agents.AI.OpenAI: 1.0.0-preview.260108.1

.NET Version

.NET 10.0

Additional Context

No response