> ## Documentation Index
> Fetch the complete documentation index at: https://docs.phidata.com/llms.txt
> Use this file to discover all available pages before exploring further.

# OpenAI

The GPT models are the best in class LLMs and used as the default LLM by **Agents**.

## Authentication

Set your `OPENAI_API_KEY` environment variable. You can get one [from OpenAI here](https://platform.openai.com/account/api-keys).

<CodeGroup>
  ```bash Mac theme={null}
  export OPENAI_API_KEY=sk-***
  ```

  ```bash Windows theme={null}
  setx OPENAI_API_KEY sk-***
  ```
</CodeGroup>

## Example

Use `OpenAIChat` with your `Agent`:

<CodeGroup>
  ```python agent.py theme={null}

  from phi.agent import Agent, RunResponse
  from phi.model.openai import OpenAIChat

  agent = Agent(
      model=OpenAIChat(id="gpt-4o"),
      markdown=True
  )

  # Get the response in a variable
  # run: RunResponse = agent.run("Share a 2 sentence horror story.")
  # print(run.content)

  # Print the response in the terminal
  agent.print_response("Share a 2 sentence horror story.")

  ```
</CodeGroup>

## Params

For more information, please refer to the [OpenAI docs](https://platform.openai.com/docs/api-reference/chat/create) as well.

<Snippet file="model-openai-params.mdx" />