Error thrown after updating package. How to fix it? [invalid_function_parameters]

[flintlouis]

Hi,
I had a simple working chat bot set up with UseFunctionInvocation enabled.
After updating I am getting a new error.

Pseudo code example:

class Foo
{
	public List<Foo> Children { get; set; } = new();
}

static Foo GetFoo() => this.foo;

static void SetFoo(Foo value) => this.foo = value;

AIFunction getFooTool = AIFunctionFactory.Create(GetFoo); // Works
AIFunction setFooTool = AIFunctionFactory.Create(SetFoo); // Error

var options = new ChatOptions
{
	Tools = [getFooTool, setFooTool],
}

var responseStream = chatClient.GetStreamingResponseAsync(chatHistory, options); // Error thrown here

After updating to:
"Microsoft.Extensions.AI" Version="9.4.0-preview.1.25207.5"
"Microsoft.Extensions.AI.OpenAI" Version="9.4.0-preview.1.25207.5"

I get this error:

Unhandled exception. System.ClientModel.ClientResultException: HTTP 400 (invalid_request_error: invalid_function_parameters)
Parameter: tools[2].function.parameters

Invalid schema for function '__Main___g__SetFoo_0_3': In context=('properties', 'value', 'properties', 'children', 'items'), reference can only point to definitions defined at the top level of the schema.
   at OpenAI.ClientPipelineExtensions.ProcessMessageAsync(ClientPipeline pipeline, PipelineMessage message, RequestOptions options)
   at OpenAI.Chat.ChatClient.CompleteChatAsync(BinaryContent content, RequestOptions options)
   at OpenAI.Chat.ChatClient.<>c__DisplayClass10_0.<<CompleteChatStreamingAsync>b__0>d.MoveNext()

I don't understand why it can return Foo but can't accept Foo as a parameter. Is this correct?
If not submitting setFooTool the program runs fine

[stephentoub]

Two things:

1. The latest release includes a change to Microsoft.Extensions.AI.OpenAI that turns on OpenAI's strict mode by default; "strict" is beneficial in that OpenAI then guarantees that the generated results will match the specific schema, but to do that they also impose more constraints on what the schema can be. In this case, the generated schema is running afoul of these constraints. We've realized that this change was a mistake and are reverting it in Disable default required property schema generation and OpenAI strict mode. #6285. In the meantime, you should be able to workaround this by changing your AIFunctionFactory.Create call to be AIFunctionFactory.Create(SetFoo, new() { AdditionalProperties = new Dictionary<string, object?>() { ["Strict"] = false }).
2. @eiriktsarpalis, is it expected that we generate a schema for this type which doesn't meet OpenAI's strict requirements?

[flintlouis]

Thankyou