microsoft/autogen · error · Exception

Please set OPENAI_API_KEY environment variable.

Error message

Please set OPENAI_API_KEY environment variable.

What it means

Startup guard in the streaming tool-call getting-started sample: before constructing OpenAIClient and the OpenAIChatAgent with streaming function-call middleware, the sample reads OPENAI_API_KEY and throws when it is absent. It fires at agent-construction time in sample code — no streaming request or weather tool call is attempted.

Source

Thrown at dotnet/samples/AgentChat/AutoGen.Basic.Sample/GettingStart/Streaming_Tool_Call.cs:30

internal class Streaming_Tool_Call
{
    public static async Task RunAsync()
    {
        #region Create_tools
        var tools = new Tools();
        #endregion Create_tools

        #region Create_auto_invoke_middleware
        var autoInvokeMiddleware = new FunctionCallMiddleware(
            functions: [tools.GetWeatherFunctionContract],
            functionMap: new Dictionary<string, Func<string, Task<string>>>()
            {
                { tools.GetWeatherFunctionContract.Name, tools.GetWeatherWrapper },
            });
        #endregion Create_auto_invoke_middleware

        #region Create_Agent
        var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new Exception("Please set OPENAI_API_KEY environment variable.");
        var model = "gpt-4o-mini";
        var openaiClient = new OpenAIClient(apiKey);
        var agent = new OpenAIChatAgent(
            chatClient: openaiClient.GetChatClient(model),
            name: "agent",
            systemMessage: "You are a helpful AI assistant")
            .RegisterMessageConnector()
            .RegisterStreamingMiddleware(autoInvokeMiddleware)
            .RegisterPrintMessage();
        #endregion Create_Agent

        IMessage finalReply = null;
        var question = new TextMessage(Role.User, "What's the weather in Seattle");

        // In streaming function call
        // function can only be invoked untill all the chunks are collected
        // therefore, only one ToolCallAggregateMessage chunk will be return here.
        await foreach (var message in agent.GenerateStreamingReplyAsync([question]))

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Set OPENAI_API_KEY in the launching shell or IDE run profile and re-run.
2. Verify with a quick environment dump that the sample process sees the variable.
3. Confirm gpt-4o-mini access on the key (the model is hard-coded).
4. Remember streaming function calls require a tool-capable model — an invalid model/key surfaces as an API error after this guard passes.

Example fix

// before
var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new Exception("Please set OPENAI_API_KEY environment variable.");

// after
var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY")
    ?? throw new InvalidOperationException("OPENAI_API_KEY is not set. Export it before running Streaming_Tool_Call.");

var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
if (string.IsNullOrWhiteSpace(apiKey))
{
    Console.Error.WriteLine("Set OPENAI_API_KEY before running Streaming_Tool_Call.");
    return;
}

try
{
    await RunAsync();
}
catch (Exception ex) when (ex.Message.Contains("OPENAI_API_KEY"))
{
    Console.Error.WriteLine($"Configuration error: {ex.Message}");
}

When it happens

Trigger: Invoking the sample's run method with OPENAI_API_KEY unset in the process. The throw precedes OpenAIClient creation, so nothing network-related has happened yet.

Common situations: Running getting-started samples without key setup; IDE debug sessions that don't inherit exported variables; only Azure OpenAI credentials configured while this sample targets the public OpenAI endpoint.

Related errors

• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/b270c2a4052b9d1e. Report an issue: GitHub.