Edit

Share via

OpenAI Integration

Note

This tutorial describes OpenAI integration in .NET apps; Integration for Python apps is in the works...

The Microsoft.Agents.AI.Hosting.OpenAI library enables you to expose AI agents through OpenAI-compatible HTTP endpoints, supporting both the Chat Completions and Responses APIs. This allows you to integrate your agents with any OpenAI-compatible client or tool.

NuGet Package:

What Are OpenAI Protocols?

The hosting library supports two OpenAI protocols:

  • Chat Completions API - Standard stateless request/response format for chat interactions
  • Responses API - Advanced format that supports conversations, streaming, and long-running agent processes

When to Use Each Protocol

The Responses API is now the default and recommended approach according to OpenAI's documentation. It provides a more comprehensive and feature-rich interface for building AI applications with built-in conversation management, streaming capabilities, and support for long-running processes.

Use the Responses API when:

  • Building new applications (recommended default)
  • You need server-side conversation management. However, that is not a requirement: you can still use Responses API in stateless mode.
  • You want persistent conversation history
  • You're building long-running agent processes
  • You need advanced streaming capabilities with detailed event types
  • You want to track and manage individual responses (e.g., retrieve a specific response by ID, check its status, or cancel a running response)

Use the Chat Completions API when:

  • Migrating existing applications that rely on the Chat Completions format
  • You need simple, stateless request/response interactions
  • State management is handled entirely by your client
  • You're integrating with existing tools that only support Chat Completions
  • You need maximum compatibility with legacy systems

Chat Completions API

The Chat Completions API provides a simple, stateless interface for interacting with agents using the standard OpenAI chat format.

Setting up an agent in ASP.NET Core with ChatCompletions integration

Here's a complete example exposing an agent via the Chat Completions API:

Prerequisites

1. Create an ASP.NET Core Web API project

Create a new ASP.NET Core Web API project or use an existing one.

2. Install required dependencies

Install the following packages:

Run the following commands in your project directory to install the required NuGet packages:

# Hosting.A2A.AspNetCore for OpenAI ChatCompletions/Responses protocol(s) integration
dotnet add package Microsoft.Agents.AI.Hosting.OpenAI --prerelease

# Libraries to connect to Azure OpenAI
dotnet add package Azure.AI.OpenAI --prerelease
dotnet add package Azure.Identity
dotnet add package Microsoft.Extensions.AI
dotnet add package Microsoft.Extensions.AI.OpenAI --prerelease

# Swagger to test app
dotnet add package Microsoft.AspNetCore.OpenApi
dotnet add package Swashbuckle.AspNetCore

3. Configure Azure OpenAI connection

The application requires an Azure OpenAI connection. Configure the endpoint and deployment name using dotnet user-secrets or environment variables. You can also simply edit the appsettings.json, but that's not recommended for the apps deployed in production since some of the data can be considered to be secret.

dotnet user-secrets set "AZURE_OPENAI_ENDPOINT" "https://<your-openai-resource>.openai.azure.com/"
dotnet user-secrets set "AZURE_OPENAI_DEPLOYMENT_NAME" "gpt-4o-mini"

4. Add the code to Program.cs

Replace the contents of Program.cs with the following code:

using Azure.AI.OpenAI;
using Azure.Identity;
using Microsoft.Agents.AI.Hosting;
using Microsoft.Extensions.AI;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddOpenApi();
builder.Services.AddSwaggerGen();

string endpoint = builder.Configuration["AZURE_OPENAI_ENDPOINT"]
    ?? throw new InvalidOperationException("AZURE_OPENAI_ENDPOINT is not set.");
string deploymentName = builder.Configuration["AZURE_OPENAI_DEPLOYMENT_NAME"]
    ?? throw new InvalidOperationException("AZURE_OPENAI_DEPLOYMENT_NAME is not set.");

// Register the chat client
IChatClient chatClient = new AzureOpenAIClient(
        new Uri(endpoint),
        new DefaultAzureCredential())
    .GetChatClient(deploymentName)
    .AsIChatClient();
builder.Services.AddSingleton(chatClient);

builder.AddOpenAIChatCompletions();

// Register an agent
var pirateAgent = builder.AddAIAgent("pirate", instructions: "You are a pirate. Speak like a pirate.");

var app = builder.Build();

app.MapOpenApi();
app.UseSwagger();
app.UseSwaggerUI();

// Expose the agent via OpenAI ChatCompletions protocol
app.MapOpenAIChatCompletions(pirateAgent);

app.Run();

Testing the Chat Completions Endpoint

Once the application is running, you can test the agent using the OpenAI SDK or HTTP requests:

Using HTTP Request

POST {{baseAddress}}/pirate/v1/chat/completions
Content-Type: application/json
{
  "model": "pirate",
  "stream": false,
  "messages": [
    {
      "role": "user",
      "content": "Hey mate!"
    }
  ]
}

Note: Replace {{baseAddress}} with your server endpoint.

Here is a sample response:

{
	"id": "chatcmpl-nxAZsM6SNI2BRPMbzgjFyvWWULTFr",
	"object": "chat.completion",
	"created": 1762280028,
	"model": "gpt-5",
	"choices": [
		{
			"index": 0,
			"finish_reason": "stop",
			"message": {
				"role": "assistant",
				"content": "Ahoy there, matey! How be ye farin' on this fine day?"
			}
		}
	],
	"usage": {
		"completion_tokens": 18,
		"prompt_tokens": 22,
		"total_tokens": 40,
		"completion_tokens_details": {
			"accepted_prediction_tokens": 0,
			"audio_tokens": 0,
			"reasoning_tokens": 0,
			"rejected_prediction_tokens": 0
		},
		"prompt_tokens_details": {
			"audio_tokens": 0,
			"cached_tokens": 0
		}
	},
	"service_tier": "default"
}

The response includes the message ID, content, and usage statistics.

Chat Completions also supports streaming, where output is returned in chunks as soon as content is available. This capability enables displaying output progressively. You can enable streaming by specifying "stream": true. The output format consists of Server-Sent Events (SSE) chunks as defined in the OpenAI Chat Completions specification.

POST {{baseAddress}}/pirate/v1/chat/completions
Content-Type: application/json
{
  "model": "pirate",
  "stream": true,
  "messages": [
    {
      "role": "user",
      "content": "Hey mate!"
    }
  ]
}

And the output we get is a set of ChatCompletions chunks:

data: {"id":"chatcmpl-xwKgBbFtSEQ3OtMf21ctMS2Q8lo93","choices":[],"object":"chat.completion.chunk","created":0,"model":"gpt-5"}

data: {"id":"chatcmpl-xwKgBbFtSEQ3OtMf21ctMS2Q8lo93","choices":[{"index":0,"finish_reason":"stop","delta":{"content":"","role":"assistant"}}],"object":"chat.completion.chunk","created":0,"model":"gpt-5"}

...

data: {"id":"chatcmpl-xwKgBbFtSEQ3OtMf21ctMS2Q8lo93","choices":[],"object":"chat.completion.chunk","created":0,"model":"gpt-5","usage":{"completion_tokens":34,"prompt_tokens":23,"total_tokens":57,"completion_tokens_details":{"accepted_prediction_tokens":0,"audio_tokens":0,"reasoning_tokens":0,"rejected_prediction_tokens":0},"prompt_tokens_details":{"audio_tokens":0,"cached_tokens":0}}}

The streaming response contains similar information, but delivered as Server-Sent Events.

Responses API

The Responses API provides advanced features including conversation management, streaming, and support for long-running agent processes.

Setting up an agent in ASP.NET Core with Responses API integration

Here's a complete example using the Responses API:

Prerequisites

Follow the same prerequisites as the Chat Completions example (steps 1-3).

4. Add the code to Program.cs

using Azure.AI.OpenAI;
using Azure.Identity;
using Microsoft.Agents.AI.Hosting;
using Microsoft.Extensions.AI;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddOpenApi();
builder.Services.AddSwaggerGen();

string endpoint = builder.Configuration["AZURE_OPENAI_ENDPOINT"]
    ?? throw new InvalidOperationException("AZURE_OPENAI_ENDPOINT is not set.");
string deploymentName = builder.Configuration["AZURE_OPENAI_DEPLOYMENT_NAME"]
    ?? throw new InvalidOperationException("AZURE_OPENAI_DEPLOYMENT_NAME is not set.");

// Register the chat client
IChatClient chatClient = new AzureOpenAIClient(
        new Uri(endpoint),
        new DefaultAzureCredential())
    .GetChatClient(deploymentName)
    .AsIChatClient();
builder.Services.AddSingleton(chatClient);

builder.AddOpenAIResponses();
builder.AddOpenAIConversations();

// Register an agent
var pirateAgent = builder.AddAIAgent("pirate", instructions: "You are a pirate. Speak like a pirate.");

var app = builder.Build();

app.MapOpenApi();
app.UseSwagger();
app.UseSwaggerUI();

// Expose the agent via OpenAI Responses protocol
app.MapOpenAIResponses(pirateAgent);
app.MapOpenAIConversations();

app.Run();

Testing the Responses API

The Responses API is similar to Chat Completions but is stateful, allowing you to pass a conversation parameter. Like Chat Completions, it supports the stream parameter, which controls the output format: either a single JSON response or a stream of events. The Responses API defines its own streaming event types, including response.created, response.output_item.added, response.output_item.done, response.completed, and others.

Create a Conversation and Response

You can send a Responses request directly, or you can first create a conversation using the Conversations API and then link subsequent requests to that conversation.

To begin, create a new conversation:

POST http://localhost:5209/v1/conversations
Content-Type: application/json
{
  "items": [
    {
        "type": "message",
        "role": "user",
        "content": "Hello!"
      }
  ]
}

The response includes the conversation ID:

{
  "id": "conv_E9Ma6nQpRzYxRHxRRqoOWWsDjZVyZfKxlHhfCf02Yxyy9N2y",
  "object": "conversation",
  "created_at": 1762881679,
  "metadata": {}
}

Next, send a request and specify the conversation parameter. (To receive the response as streaming events, set "stream": true in the request.)

POST http://localhost:5209/pirate/v1/responses
Content-Type: application/json
{
  "stream": false,
  "conversation": "conv_E9Ma6nQpRzYxRHxRRqoOWWsDjZVyZfKxlHhfCf02Yxyy9N2y",
  "input": [
    {
      "type": "message",
      "role": "user",
      "content": [
        {
            "type": "input_text",
            "text": "are you a feminist?"
        }
      ]
    }
  ]
}

The agent returns the response and saves the conversation items to storage for later retrieval:

{
  "id": "resp_FP01K4bnMsyQydQhUpovK6ysJJroZMs1pnYCUvEqCZqGCkac",
  "conversation": "conv_E9Ma6nQpRzYxRHxRRqoOWWsDjZVyZfKxlHhfCf02Yxyy9N2y",
  "object": "response",
  "created_at": 1762881518,
  "status": "completed",
  "incomplete_details": null,
  "output": [
    {
      "role": "assistant",
      "content": [
        {
          "type": "output_text",
          "text": "Arrr, matey! As a pirate, I be all about respect for the crew, no matter their gender! We sail these seas together, and every hand on deck be valuable. A true buccaneer knows that fairness and equality be what keeps the ship afloat. So, in me own way, I’d say I be supportin’ all hearty souls who seek what be right! What say ye?"
        }
      ],
      "type": "message",
      "status": "completed",
      "id": "msg_1FAQyZcWgsBdmgJgiXmDyavWimUs8irClHhfCf02Yxyy9N2y"
    }
  ],
  "usage": {
    "input_tokens": 26,
    "input_tokens_details": {
      "cached_tokens": 0
    },
    "output_tokens": 85,
    "output_tokens_details": {
      "reasoning_tokens": 0
    },
    "total_tokens": 111
  },
  "tool_choice": null,
  "temperature": 1,
  "top_p": 1  
}

The response includes conversation and message identifiers, content, and usage statistics.

To retrieve the conversation items, send this request:

GET http://localhost:5209/v1/conversations/conv_E9Ma6nQpRzYxRHxRRqoOWWsDjZVyZfKxlHhfCf02Yxyy9N2y/items?include=string

This returns a JSON response containing both input and output messages:

{
  "object": "list",
  "data": [
    {
      "role": "assistant",
      "content": [
        {
          "type": "output_text",
          "text": "Arrr, matey! As a pirate, I be all about respect for the crew, no matter their gender! We sail these seas together, and every hand on deck be valuable. A true buccaneer knows that fairness and equality be what keeps the ship afloat. So, in me own way, I’d say I be supportin’ all hearty souls who seek what be right! What say ye?",
          "annotations": [],
          "logprobs": []
        }
      ],
      "type": "message",
      "status": "completed",
      "id": "msg_1FAQyZcWgsBdmgJgiXmDyavWimUs8irClHhfCf02Yxyy9N2y"
    },
    {
      "role": "user",
      "content": [
        {
          "type": "input_text",
          "text": "are you a feminist?"
        }
      ],
      "type": "message",
      "status": "completed",
      "id": "msg_iLVtSEJL0Nd2b3ayr9sJWeV9VyEASMlilHhfCf02Yxyy9N2y"
    }
  ],
  "first_id": "msg_1FAQyZcWgsBdmgJgiXmDyavWimUs8irClHhfCf02Yxyy9N2y",
  "last_id": "msg_lUpquo0Hisvo6cLdFXMKdYACqFRWcFDrlHhfCf02Yxyy9N2y",
  "has_more": false
}

Exposing Multiple Agents

You can expose multiple agents simultaneously using both protocols:

var mathAgent = builder.AddAIAgent("math", instructions: "You are a math expert.");
var scienceAgent = builder.AddAIAgent("science", instructions: "You are a science expert.");

// Add both protocols
builder.AddOpenAIChatCompletions();
builder.AddOpenAIResponses();

var app = builder.Build();

// Expose both agents via Chat Completions
app.MapOpenAIChatCompletions(mathAgent);
app.MapOpenAIChatCompletions(scienceAgent);

// Expose both agents via Responses
app.MapOpenAIResponses(mathAgent);
app.MapOpenAIResponses(scienceAgent);

Agents will be available at:

  • Chat Completions: /math/v1/chat/completions and /science/v1/chat/completions
  • Responses: /math/v1/responses and /science/v1/responses

Custom Endpoints

You can customize the endpoint paths:

// Custom path for Chat Completions
app.MapOpenAIChatCompletions(mathAgent, path: "/api/chat");

// Custom path for Responses
app.MapOpenAIResponses(scienceAgent, responsesPath: "/api/responses");

See Also

  • Last updated on