Azure OpenAI: Wrong API status code formatting

Question

The Azure OpenAI Service returns a validation error for certain inputs for the ChatCompleteAsync Api, the response looks similar to:

{
    "requestid": "1b7cfa98-de62-440f-b230-72919bfa42a0",
    "code": 400,
    "message": "Validation error at #/max_completion_tokens: Extra inputs are not permitted"
}

The .NET SDK expects the "code" property to be a string and the parsing throws an exception

System.InvalidOperationException
  HResult=0x80131509
  Message=The requested operation requires an element of type 'String', but the target element has type 'Number'.
  Source=System.Text.Json
  StackTrace:
   at System.Text.Json.ThrowHelper.ThrowJsonElementWrongTypeException(JsonTokenType expectedType, JsonTokenType actualType) in System.Text.Json\ThrowHelper.cs:line 288

The unfortunate side effect of this exception is, that this exception is caught and a generic BadRequestException is thrown, which does not contain the details anymore. You have to enable break on all exception in Visual Studio to actually see the relevant exception.

I opened an issue on the OpenAI SDK github for it but the OpenAI team responded, that the parser is correct and the schema requires the "code" property to be a string and that I should open an issue here as this needs to be fixed on Azure's side.

See: https://github.com/openai/openai-dotnet/issues/669 for the full history

A full repro of the probem:

// use with reasoning model, e.g. gpt-5-mini, enable Break on all Exceptions
using System.ClientModel;
using System.ClientModel.Primitives;
using System.Text.Json;
using Azure.AI.OpenAI;
using Azure.AI.OpenAI.Chat;
using OpenAI;
using OpenAI.Assistants;
using OpenAI.Chat;

namespace ConsoleApp3
{
    internal class Program
    {
        static async Task Main(string[] args)
        {
            const string openAiEndpoint = "https://your_ai_endpoint.openai.azure.com/";
            const string openAiKey = "Key";
            const string searchEndpoint = "https://does_not_matter.search.windows.net";
            const string indexName = "vector";
            const string searchKey = "Key";
            const string semanticConfiguration = "vector-semantic-configuration";
            const string embeddingId = "text-embedding-3-small";
            const string modelDeploymentId = "gpt-5-mini";

            using var cts = new CancellationTokenSource();

            var aiClientOptions = new AzureOpenAIClientOptions
            {
                RetryPolicy = new ClientRetryPolicy()
            };
            var client = new AzureOpenAIClient(new Uri(openAiEndpoint), new ApiKeyCredential(openAiKey), aiClientOptions);

            var chatCompletionsOptions = new ChatCompletionOptions
            {
                MaxOutputTokenCount = 500,
            };
#pragma warning disable AOAI001
            // the actual values do not matter here, it's only populated to trigger the exception
            var chatDataSource = new AzureSearchChatDataSource
            {
                Endpoint = new Uri(searchEndpoint),
                IndexName = indexName,
                InScope = true,
                QueryType = DataSourceQueryType.VectorSemanticHybrid,
                Authentication = DataSourceAuthentication.FromApiKey(searchKey),
                SemanticConfiguration = semanticConfiguration,
                VectorizationSource = DataSourceVectorizer.FromDeploymentName(embeddingId)
            };
            chatCompletionsOptions.AddDataSource(chatDataSource); // this triggers the exception
            chatCompletionsOptions.SetNewMaxCompletionTokensPropertyEnabled();
#pragma warning restore AOAI001
            var chatClient = client.GetChatClient(modelDeploymentId);
            var systemChatMessage = new SystemChatMessage("You're a nice AI agent.");
            var userMessage = new UserChatMessage("Hello World");
            // this will now throw, enable break on all Exceptions,so it breaks already on the System.InvalidOperationException
            // 'The requested operation requires an element of type 'String', but the target element has type 'Number'.'
            var completion = await chatClient.CompleteChatAsync([systemChatMessage, userMessage], chatCompletionsOptions, cts.Token).ConfigureAwait(false);
        }
    }
}