---
title: "Overview"
source: Microsoft AutoGen
source_url: https://github.com/microsoft/autogen
licence: CC-BY-4.0
domain: agentic-ai
subdomain: autogen-docs
date_added: 2026-04-25
---

The following example shows how to connect to third-party OpenAI API using @AutoGen.OpenAI.OpenAIChatAgent.


## Overview
A lot of LLM applications/platforms support spinning up a chat server that is compatible with OpenAI API, such as LM Studio, Ollama, Mistral etc. This means that you can connect to these servers using the @AutoGen.OpenAI.OpenAIChatAgent.

> [!NOTE]
> Some platforms might not support all the features of OpenAI API. For example, Ollama does not support `function call` when using it's openai API according to its [document](https://github.com/ollama/ollama/blob/main/docs/openai.md#v1chatcompletions) (as of 2024/05/07).
> That means some of the features of OpenAI API might not work as expected when using these platforms with the @AutoGen.OpenAI.OpenAIChatAgent.
> Please refer to the platform's documentation for more information.

## Prerequisites
- Install the following packages:
```bash
dotnet add package AutoGen.OpenAI --version AUTOGEN_VERSION
```

- Spin up a chat server that is compatible with OpenAI API.
The following example uses Ollama as the chat server, and llama3 as the llm model.
```bash
ollama serve
```

## Steps
- Import the required namespaces:
[!code-csharp[](../../samples/AutoGen.OpenAI.Sample/Connect_To_Ollama.cs?name=using_statement)]

- Create a `CustomHttpClientHandler` class.

The `CustomHttpClientHandler` class is used to customize the HttpClientHandler. In this example, we override the `SendAsync` method to redirect the request to local Ollama server, which is running on `http://localhost:11434`.

[!code-csharp[](../../samples/AutoGen.OpenAI.Sample/Connect_To_Ollama.cs?name=CustomHttpClientHandler)]

- Create an `OpenAIChatAgent` instance and connect to the third-party API.

Then create an @AutoGen.OpenAI.OpenAIChatAgent instance and connect to the OpenAI API from Ollama. You can customize the transport behavior of `OpenAIClient` by passing a customized `HttpClientTransport` instance. In the customized `HttpClientTransport` instance, we pass the `CustomHttpClientHandler` we just created which redirects all openai chat requests to the local Ollama server.

[!code-csharp[](../../samples/AutoGen.OpenAI.Sample/Connect_To_Ollama.cs?name=create_agent)]

- Chat with the `OpenAIChatAgent`.
Finally, you can start chatting with the agent. In this example, we send a coding question to the agent and get the response.

[!code-csharp[](../../samples/AutoGen.OpenAI.Sample/Connect_To_Ollama.cs?name=send_message)]

## Sample Output
The following is the sample output of the code snippet above:

![output](../images/articles/ConnectTo3PartyOpenAI/output.gif)
