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

# Cartesia

[Cartesia](https://cartesia.ai/?utm_medium=partner\&utm_source=getstream) provides low-latency text-to-speech with the Sonic model. Designed for real-time voice applications with natural-sounding speech synthesis.

<Info>
  Vision Agents requires a [Stream](https://getstream.io/try-for-free/) account
  for real-time transport. Most providers offer free tiers to get started.
</Info>

## Installation

```sh theme={null}
uv add "vision-agents[cartesia]"
```

## Quick Start

```python theme={null}
from vision_agents.core import Agent, User
from vision_agents.plugins import cartesia, gemini, deepgram, getstream

agent = Agent(
    edge=getstream.Edge(),
    agent_user=User(name="Assistant", id="agent"),
    instructions="You are a helpful assistant.",
    llm=gemini.LLM("gemini-3-flash-preview"),
    stt=deepgram.STT(),
    tts=cartesia.TTS(),
)
```

<Warning>
  Set `CARTESIA_API_KEY` in your environment or pass `api_key` directly.
</Warning>

## Parameters

| Name          | Type  | Default                                  | Description                                      |
| ------------- | ----- | ---------------------------------------- | ------------------------------------------------ |
| `model_id`    | `str` | `"sonic-3"`                              | Cartesia TTS model                               |
| `voice_id`    | `str` | `"f9836c6e-a0bd-460e-9d3c-f7299fa60f94"` | Voice ID                                         |
| `sample_rate` | `int` | `16000`                                  | Audio sample rate in Hz                          |
| `api_key`     | `str` | `None`                                   | API key (defaults to `CARTESIA_API_KEY` env var) |

## Next Steps

<CardGroup cols={2}>
  <Card title="Build a Voice Agent" icon="microphone" href="/introduction/voice-agents">
    Get started with voice
  </Card>

  <Card title="Build a Video Agent" icon="video" href="/introduction/video-agents">
    Add video processing
  </Card>
</CardGroup>