Cartesia is a service that provides Speech-to-Text (STT) and Text-to-Speech (TTS) capabilities. It’s designed for real-time voice applications, making it ideal for voice AI agents, transcription pipelines, and conversational interfaces.
The Cartesia plugin for the Stream Python AI SDK allows you to add TTS functionality to your project.
Installation
Install the Stream Cartesia plugin with
uv add vision-agents[cartesia]
Example
Check out our Cartesia example to see a working code sample using the plugin, or read on for some key details.
Initialisation
The Cartesia plugin for Stream exists in the form of the TTS class:
from vision_agents.plugins import cartesia
tts = cartesia.TTS()
To initialise without passing in the API key, make sure the CARTESIA_API_KEY is available as an environment variable.
You can do this either by defining it in a .env file or exporting it directly in your terminal.
Parameters
These are the parameters available in the CartesiaTTS plugin for you to customise:
| Name | Type | Default | Description |
|---|
api_key | str or None | None | Your Cartesia API key. If not provided, the plugin will look for the CARTESIA_API_KEY environment variable. |
model_id | str | "sonic-3" | ID of the Cartesia STT or TTS model to use. Defaults to the recently released Sonic-3 |
voice_id | str or None | "f9836c6e-a0bd-460e-9d3c-f7299fa60f94" | ID of the voice to use for TTS responses. |
sample_rate | int | 16000 | Sample rate (in Hz) used for audio processing. |
Functionality
Send text to convert to speech
The send() method sends the text passed in for the service to synthesize.
The resulting audio is then played through the configured output track.
tts.send("Demo text you want AI voice to say")
