OpenAI Provider

Connect to the OpenAI API (api.openai.com) for chat completions, embeddings, image generation, and speech.

Quick Start

builder.Services
    .AddCoreAIServices()
    .AddCoreAIOrchestration()
    .AddCoreAIOpenAI();

Services Registered

Service	Implementation	Lifetime
IAIClientProvider	OpenAIClientProvider	Scoped
IAICompletionClient	OpenAICompletionClient	Scoped
Connection source	—	Scoped

Configuration

Connection Setup

Provide an API key through your connection source:

builder.Services.AddCoreAIConnectionSource("OpenAI", options =>
{
    options.Connections.Add(new AIProviderConnectionEntry
    {
        Name = "my-openai",
        ProviderName = "OpenAI",
        // Set API key and optional endpoint
    });
});

Constants

Constant	Value
OpenAIConstants.ProviderName	"OpenAI"
OpenAIConstants.ClientName	"OpenAI"

Capabilities

Capability	Supported
Chat completions	✅
Streaming	✅
Embeddings	✅
Image generation	✅
Speech-to-text	✅
Text-to-speech	✅

Configuration Example

A full appsettings.json configuration for OpenAI:

{
  "CrestApps": {
    "AI": {
      "Providers": {
        "OpenAI": {
          "ApiKey": "sk-..."
        }
      }
    }
  }
}

Or register connections programmatically:

builder.Services.AddCoreAIConnectionSource("OpenAI", options =>
{
    options.Connections.Add(new AIProviderConnectionEntry
    {
        Name = "my-openai",
        ProviderName = "OpenAI",
        // API key is read from configuration or set directly
    });
});

tip

Never commit API keys to source control. Use environment variables, user secrets, or a vault provider:

dotnet user-secrets set "CrestApps:AI:Providers:OpenAI:ApiKey" "sk-..."

Available Models

Model	Type	Context Window	Best For
gpt-4.1	Chat	1M tokens	Complex reasoning, coding, instruction following
gpt-4.1-mini	Chat	1M tokens	Balanced performance and cost
gpt-4.1-nano	Chat	1M tokens	Fast, cost-effective for simple tasks
o4-mini	Reasoning	200K tokens	STEM, math, coding with chain-of-thought
gpt-4o	Chat	128K tokens	Multimodal (text + vision), general purpose
gpt-4o-mini	Chat	128K tokens	Budget-friendly multimodal
text-embedding-3-small	Embedding	8K tokens	Cost-effective embeddings
text-embedding-3-large	Embedding	8K tokens	Higher-quality embeddings
dall-e-3	Image	—	Image generation
whisper-1	Speech-to-text	—	Audio transcription
tts-1 / tts-1-hd	Text-to-speech	—	Voice synthesis

info

Model availability and capabilities change frequently. Check the OpenAI models documentation for the latest information.

Streaming

The OpenAI provider fully supports streaming responses. When streaming is enabled, tokens are sent to the client as they are generated rather than waiting for the complete response:

// Streaming is handled automatically by the orchestrator when the
// chat interaction is configured for streaming (the default for real-time chat).
// No additional configuration is needed.

Streaming is the default behavior for the chat interactions module. The OpenAICompletionClient uses the IChatClient.GetStreamingResponseAsync() method from the Microsoft.Extensions.AI abstraction.

Function Calling

OpenAI models support function calling (tool use), which is the foundation for the Custom AI Tools system. When tools are registered and assigned to a profile, the OpenAI provider automatically:

1. Serializes tool definitions as JSON Schema in the request
2. Parses tool call responses from the model
3. Invokes the matching AITool via the orchestrator
4. Sends tool results back to the model for the final response

All GPT-4 and newer models support parallel function calling (multiple tools invoked in a single turn).