Skip to main content
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:
NameTypeDefaultDescription
api_keystr or NoneNoneYour Cartesia API key. If not provided, the plugin will look for the CARTESIA_API_KEY environment variable.
model_idstr"sonic-2"ID of the Cartesia STT or TTS model to use.
voice_idstr or None"f9836c6e-a0bd-460e-9d3c-f7299fa60f94"ID of the voice to use for TTS responses.
sample_rateint16000Sample 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")
⌘I