OpenAI

Features 🔥

• Fully generated C# SDK based on official OpenAI OpenAPI specification using AutoSDK
• Same day update to support new features
• Updated and supported automatically if there are no breaking changes
• Contains a supported list of constants such as current prices, models, and other
• Source generator to define functions natively through C# interfaces
• All modern .NET features - nullability, trimming, NativeAOT, etc.
• Support .Net Framework/.Net Standard 2.0
• Support all OpenAI API endpoints including completions, chat, embeddings, images, assistants and more.
• Regularly tested for compatibility with popular custom providers like OpenRouter/DeepSeek/Ollama/LM Studio and many others
• Microsoft.Extensions.AI IChatClient and IEmbeddingGenerator support for OpenAI and all CustomProviders

Documentation

Examples and documentation can be found here: https://tryagi.github.io/OpenAI/

Usage

using var api = new OpenAiApi("API_KEY");
string response = await api.Chat.CreateChatCompletionAsync(
    messages: ["Generate five random words."],
    model: ModelIdsSharedEnum.Gpt4oMini);
Console.WriteLine(response); // "apple, banana, cherry, date, elderberry"

var enumerable = api.Chat.CreateChatCompletionAsStreamAsync(
    messages: ["Generate five random words."],
    model: ModelIdsSharedEnum.Gpt4oMini);

await foreach (string response in enumerable)
{
    Console.WriteLine(response);
}

It uses three implicit conversions:

• from string to ChatCompletionRequestUserMessage. It will always be converted to the user message.
• from ChatCompletionResponseMessage to string . It will always contain the first choice message content.
• from CreateChatCompletionStreamResponse to string . It will always contain the first delta content.

You still can use the full response objects if you need more information, just replace string response to var response.

Tools

using OpenAI;
using CSharpToJsonSchema;

public enum Unit
{
    Celsius,
    Fahrenheit,
}

public class Weather
{
    public string Location { get; set; } = string.Empty;
    public double Temperature { get; set; }
    public Unit Unit { get; set; }
    public string Description { get; set; } = string.Empty;
}

[GenerateJsonSchema(Strict = true)] // false by default. You can't use parameters with default values in Strict mode.
public interface IWeatherFunctions
{
    [Description("Get the current weather in a given location")]
    public Task<Weather> GetCurrentWeatherAsync(
        [Description("The city and state, e.g. San Francisco, CA")] string location,
        Unit unit,
        CancellationToken cancellationToken = default);
}

public class WeatherService : IWeatherFunctions
{
    public Task<Weather> GetCurrentWeatherAsync(string location, Unit unit = Unit.Celsius, CancellationToken cancellationToken = default)
    {
        return Task.FromResult(new Weather
        {
            Location = location,
            Temperature = 22.0,
            Unit = unit,
            Description = "Sunny",
        });
    }
}

using var api = new OpenAiApi("API_KEY");

var service = new WeatherService();
var tools = service.AsTools().AsOpenAiTools();

var messages = new List<ChatCompletionRequestMessage>
{
    "You are a helpful weather assistant.".AsSystemMessage(),
    "What is the current temperature in Dubai, UAE in Celsius?".AsUserMessage(),
};
var model = ModelIdsSharedEnum.Gpt4oMini;
var result = await api.Chat.CreateChatCompletionAsync(
    messages,
    model: model,
    tools: tools);
var resultMessage = result.Choices.First().Message;
messages.Add(resultMessage.AsRequestMessage());

foreach (var call in resultMessage.ToolCalls)
{
    var json = await service.CallAsync(
        functionName: call.Function.Name,
        argumentsAsJson: call.Function.Arguments);
    messages.Add(json.AsToolMessage(call.Id));
}

var result = await api.Chat.CreateChatCompletionAsync(
    messages,
    model: model,
    tools: tools);
var resultMessage = result.Choices.First().Message;
messages.Add(resultMessage.AsRequestMessage());

> System: 
You are a helpful weather assistant.
> User: 
What is the current temperature in Dubai, UAE in Celsius?
> Assistant: 
call_3sptsiHzKnaxF8bs8BWxPo0B:
GetCurrentWeather({"location":"Dubai, UAE","unit":"celsius"})
> Tool(call_3sptsiHzKnaxF8bs8BWxPo0B):
{"location":"Dubai, UAE","temperature":22,"unit":"celsius","description":"Sunny"}
> Assistant: 
The current temperature in Dubai, UAE is 22°C with sunny weather.

Structured Outputs

using OpenAI;

using var api = new OpenAiApi("API_KEY");

var response = await api.Chat.CreateChatCompletionAsAsync<Weather>(
    messages: ["Generate random weather."],
    model: ModelIdsSharedEnum.Gpt4oMini,
    jsonSerializerOptions: new JsonSerializerOptions
    {
        Converters = {new JsonStringEnumConverter()},
    });
// or (if you need trimmable/NativeAOT version)
var response = await api.Chat.CreateChatCompletionAsAsync(
    jsonTypeInfo: SourceGeneratedContext.Default.Weather,
    messages: ["Generate random weather."],
    model: ModelIdsSharedEnum.Gpt4oMini);

// response.Value1 contains the structured output
// response.Value2 contains the CreateChatCompletionResponse object

Weather:
Location: San Francisco, CA
Temperature: 65
Unit: Fahrenheit
Description: Partly cloudy with a light breeze and occasional sunshine.
Raw Response:
{"Location":"San Francisco, CA","Temperature":65,"Unit":"Fahrenheit","Description":"Partly cloudy with a light breeze and occasional sunshine."}

Additional code for trimmable/NativeAOT version:

[JsonSourceGenerationOptions(Converters = [typeof(JsonStringEnumConverter<Unit>)])]
[JsonSerializable(typeof(Weather))]
public partial class SourceGeneratedContext : JsonSerializerContext;

Custom providers

using OpenAI;

using var api = CustomProviders.GitHubModels("GITHUB_TOKEN");
using var api = CustomProviders.Azure("API_KEY", "ENDPOINT");
using var api = CustomProviders.DeepInfra("API_KEY");
using var api = CustomProviders.Groq("API_KEY");
using var api = CustomProviders.XAi("API_KEY");
using var api = CustomProviders.DeepSeek("API_KEY");
using var api = CustomProviders.Fireworks("API_KEY");
using var api = CustomProviders.OpenRouter("API_KEY");
using var api = CustomProviders.Together("API_KEY");
using var api = CustomProviders.Perplexity("API_KEY");
using var api = CustomProviders.SambaNova("API_KEY");
using var api = CustomProviders.Mistral("API_KEY");
using var api = CustomProviders.Codestral("API_KEY");
using var api = CustomProviders.Cerebras("API_KEY");
using var api = CustomProviders.Cohere("API_KEY");
using var api = CustomProviders.Ollama();
using var api = CustomProviders.LmStudio();

Microsoft.Extensions.AI

The client natively implements IChatClient and IEmbeddingGenerator<string, Embedding<float>> from Microsoft.Extensions.AI, providing a unified interface across 15+ providers:

using OpenAI;
using Microsoft.Extensions.AI;

// Works with OpenAI and all CustomProviders (Azure, DeepSeek, Groq, etc.)
using var client = new OpenAiClient("API_KEY");
// or: using var client = CustomProviders.Groq("API_KEY");

// IChatClient
IChatClient chatClient = client;
var response = await chatClient.GetResponseAsync(
    "Say hello!",
    new ChatOptions { ModelId = "gpt-4o-mini" });
Console.WriteLine(response.Messages[0].Text);

// Streaming
await foreach (var update in chatClient.GetStreamingResponseAsync(
    "Count to 5.",
    new ChatOptions { ModelId = "gpt-4o-mini" }))
{
    Console.Write(string.Concat(update.Contents.OfType<TextContent>().Select(c => c.Text)));
}

// IEmbeddingGenerator
IEmbeddingGenerator<string, Embedding<float>> generator = client;
var embeddings = await generator.GenerateAsync(
    ["Hello, world!"],
    new EmbeddingGenerationOptions { ModelId = "text-embedding-3-small" });

Constants

All tryGetXXX methods return null if the value is not found.
There also non-try methods that throw an exception if the value is not found.

using OpenAI;

// You can try to get the enum from string using:
var model = ModelIdsSharedEnumExtensions.ToEnum("gpt-4o") ?? throw new Exception("Invalid model");

// Chat
var model = ModelIdsSharedEnum.Gpt4oMini;
double? priceInUsd = model.TryGetPriceInUsd(
    inputTokens: 500,
    outputTokens: 500)
double? priceInUsd = model.TryGetFineTunePriceInUsd(
    trainingTokens: 500,
    inputTokens: 500,
    outputTokens: 500)
int contextLength = model.TryGetContextLength() // 128_000
int outputLength = model.TryGetOutputLength() // 16_000

// Embeddings
var model = CreateEmbeddingRequestModel.TextEmbedding3Small;
int? maxInputTokens = model.TryGetMaxInputTokens() // 8191
double? priceInUsd = model.TryGetPriceInUsd(tokens: 500)

// Images
double? priceInUsd = CreateImageRequestModel.DallE3.TryGetPriceInUsd(
    size: CreateImageRequestSize.x1024x1024,
    quality: CreateImageRequestQuality.Hd)

// Speech to Text
double? priceInUsd = CreateTranscriptionRequestModel.Whisper1.TryGetPriceInUsd(
    seconds: 60)

// Text to Speech
double? priceInUsd = CreateSpeechRequestModel.Tts1Hd.TryGetPriceInUsd(
    characters: 1000)

Chat Completion

Send a simple chat completion request.

using var client = new OpenAiClient(apiKey);

string response = await client.Chat.CreateChatCompletionAsync(
    new CreateChatCompletionRequest
    {
        Value2 = new CreateChatCompletionRequestVariant2
        {
            Messages = ["Generate five random words."],
            Model = "gpt-4o-mini",
        }
    });

Console.WriteLine(response);

Chat Completion Streaming

Stream a chat completion response token by token.

using var client = new OpenAiClient(apiKey);

var enumerable = client.Chat.CreateChatCompletionAsStreamAsync(
    new CreateChatCompletionRequest
    {
        Value2 = new CreateChatCompletionRequestVariant2
        {
            Messages = ["Generate five random words."],
            Model = "gpt-4o-mini",
        }
    });

await foreach (string response in enumerable)
{
    Console.Write(response);
}

Chat With Vision

Send an image to the model for analysis.

using var client = new OpenAiClient(apiKey);

CreateChatCompletionResponse response = await client.Chat.CreateChatCompletionAsync(
    new CreateChatCompletionRequest
    {
        Value2 = new CreateChatCompletionRequestVariant2
        {
            Messages = [
                "Please describe the following image.",
                H.Resources.images_dog_and_cat_png.AsBytes().AsUserMessage(mimeType: "image/png"),
            ],
            Model = "gpt-4o-mini",
        }
    });

Console.WriteLine(response.Choices[0].Message.Content);

JSON Response Format

Request a response in JSON format.

using var client = new OpenAiClient(apiKey);

string response = await client.Chat.CreateChatCompletionAsync(
    new CreateChatCompletionRequest
    {
        Value2 = new CreateChatCompletionRequestVariant2
        {
            Messages = ["Generate five random words as json."],
            Model = "gpt-4o-mini",
            ResponseFormat = new ResponseFormatJsonObject
            {
                Type = ResponseFormatJsonObjectType.JsonObject,
            },
        }
    });

Console.WriteLine(response);

Structured Outputs

Get structured JSON responses using a C# type as the schema.

using var client = new OpenAiClient(apiKey);

var response = await client.Chat.CreateChatCompletionAsAsync<WordsResponse>(
    messages: ["Generate five random words as json."],
    model: "gpt-4o-mini");

Console.WriteLine("Words:");
foreach (var word in response.Value1!.Words)
{
    Console.WriteLine(word);
}

Structured Outputs (AOT)

Get structured JSON responses using a JsonTypeInfo for AOT/trimming compatibility.

using var client = new OpenAiClient(apiKey);

var response = await client.Chat.CreateChatCompletionAsAsync(
    jsonTypeInfo: SourceGeneratedContext.Default.WordsResponse,
    messages: ["Generate five random words."],
    model: "gpt-4o-mini");

Console.WriteLine("Words:");
foreach (var word in response.Value1!.Words)
{
    Console.WriteLine(word);
}

Embeddings

Create a text embedding vector.

using var client = new OpenAiClient(apiKey);

var response = await client.Embeddings.CreateEmbeddingAsync(
    input: "Hello, world",
    model: CreateEmbeddingRequestModel.TextEmbedding3Small);

foreach (var data in response.Data.ElementAt(0).Embedding1)
{
    Console.WriteLine($"{data}");
}

Image Generation

Generate an image from a text prompt.

using var client = new OpenAiClient(apiKey);

var response = await client.Images.CreateImageAsync(
    prompt: "a white siamese cat",
    model: CreateImageRequestModel.GptImage1Mini,
    n: 1,
    quality: CreateImageRequestQuality.Low,
    size: CreateImageRequestSize.x1024x1024,
    outputFormat: CreateImageRequestOutputFormat.Png);

var base64 = response.Data?.ElementAt(0).B64Json;

Console.WriteLine($"Generated image ({base64?.Length} base64 chars)");

Text To Speech

Convert text to speech audio using streaming.

using var client = new OpenAiClient(apiKey);

using var memoryStream = new MemoryStream();
await foreach (var streamEvent in client.Audio.CreateSpeechAsync(
    model: CreateSpeechRequestModel.Gpt4oMiniTts,
    input: "Hello! This is a text-to-speech test.",
    voice: (VoiceIdsShared)VoiceIdsSharedEnum.Alloy,
    responseFormat: CreateSpeechRequestResponseFormat.Mp3,
    speed: 1.0,
    streamFormat: CreateSpeechRequestStreamFormat.Sse))
{
    if (streamEvent.SpeechAudioDelta is { } delta)
    {
        byte[] chunk = Convert.FromBase64String(delta.Audio);
        memoryStream.Write(chunk, 0, chunk.Length);
    }
}

byte[] audio = memoryStream.ToArray();

Console.WriteLine($"Generated {audio.Length} bytes of audio.");

List Models

List all available models.

using var client = new OpenAiClient(apiKey);

var models = await client.Models.ListModelsAsync();

foreach (var model in models.Data)
{
    Console.WriteLine(model.Id);
}

Moderation

Check text for policy violations using the moderation endpoint.

using var client = new OpenAiClient(apiKey);

var response = await client.Moderations.CreateModerationAsync(
    input: "Hello, world",
    model: CreateModerationRequestModel.OmniModerationLatest);

Console.WriteLine($"Flagged: {response.Results.First().Flagged}");

MEAI Chat Completion

Use the Microsoft.Extensions.AI IChatClient interface for chat completions.

using var client = new OpenAiClient(apiKey);

// using Meai = Microsoft.Extensions.AI;
Meai.IChatClient chatClient = client;

var messages = new List<Meai.ChatMessage>
{
    new(Meai.ChatRole.User, "Say hello in exactly 3 words."),
};

var response = await chatClient.GetResponseAsync(
    messages,
    new Meai.ChatOptions { ModelId = "gpt-4o-mini" });

Console.WriteLine(response.Messages[0].Text);

MEAI Chat Streaming

Stream a chat completion using the Microsoft.Extensions.AI IChatClient interface.

using var client = new OpenAiClient(apiKey);

// using Meai = Microsoft.Extensions.AI;
Meai.IChatClient chatClient = client;

var messages = new List<Meai.ChatMessage>
{
    new(Meai.ChatRole.User, "Count from 1 to 5."),
};

await foreach (var update in chatClient.GetStreamingResponseAsync(
    messages,
    new Meai.ChatOptions { ModelId = "gpt-4o-mini" }))
{
    var text = string.Concat(update.Contents.OfType<Meai.TextContent>().Select(c => c.Text));
    if (!string.IsNullOrEmpty(text))
    {
        Console.Write(text);
    }
}

MEAI Tool Calling

Use function/tool calling via the Microsoft.Extensions.AI IChatClient interface.

using var client = new OpenAiClient(apiKey);

// using Meai = Microsoft.Extensions.AI;
Meai.IChatClient chatClient = client;

var tool = Meai.AIFunctionFactory.Create(
    (string city) => city switch
    {
        "Paris" => "22C, sunny",
        "London" => "15C, cloudy",
        _ => "Unknown",
    },
    name: "GetWeather",
    description: "Gets the current weather for a city");

var chatOptions = new Meai.ChatOptions
{
    ModelId = "gpt-4o-mini",
    Tools = [tool],
};

var messages = new List<Meai.ChatMessage>
{
    new(Meai.ChatRole.User, "What's the weather in Paris? Respond with the temperature only."),
};

// First turn: get tool call
var response = await chatClient.GetResponseAsync(
    (IEnumerable<Meai.ChatMessage>)messages, chatOptions);

var functionCall = response.Messages
    .SelectMany(m => m.Contents)
    .OfType<Meai.FunctionCallContent>()
    .First();

// Execute tool and add result
var toolResult = await tool.InvokeAsync(
    functionCall.Arguments is { } args
        ? new Meai.AIFunctionArguments(args)
        : null);
messages.AddRange(response.Messages);
messages.Add(new Meai.ChatMessage(Meai.ChatRole.Tool,
    new Meai.AIContent[]
    {
        new Meai.FunctionResultContent(functionCall.CallId, toolResult),
    }));

// Second turn: get final response
var finalResponse = await chatClient.GetResponseAsync(
    (IEnumerable<Meai.ChatMessage>)messages, chatOptions);

Console.WriteLine(finalResponse.Messages[0].Text);

MEAI Embeddings

Generate embeddings using the Microsoft.Extensions.AI IEmbeddingGenerator interface.

using var client = new OpenAiClient(apiKey);

// using Meai = Microsoft.Extensions.AI;
Meai.IEmbeddingGenerator<string, Meai.Embedding<float>> generator = client;

var result = await generator.GenerateAsync(
    new List<string> { "Hello, world!" },
    new Meai.EmbeddingGenerationOptions
    {
        ModelId = "text-embedding-3-small",
    });

Console.WriteLine($"Embedding dimension: {result[0].Vector.Length}");

Support

Priority place for bugs: https://github.com/tryAGI/OpenAI/issues
Priority place for ideas and general questions: https://github.com/tryAGI/OpenAI/discussions
Discord: https://discord.gg/Ca2xhfBf3v

Acknowledgments

This project is supported by JetBrains through the Open Source Support Program.