Where it fits
Speech synthesis
A voice sample alone does not predict telephone quality. Test your actual carrier and language, and review the provider’s usage units.
Configure the connection
Select a Cartesia voice ID in the assistant’s speech settings. Keep the STT and LLM stages explicit so changing voice does not change the rest of the pipeline.
Assistant configuration fragment. Merge this into your assistant; select current model and voice IDs from your account before saving.
{
"pipeline_mode": "cascading",
"tts_provider": "cartesia",
"tts_voice": "YOUR_CARTESIA_VOICE_ID"
}Keep provider secrets in workspace credentials. The public MCP provider matrix describes capabilities; it does not connect your provider account.
Test this boundary first
Compare the same script across voices. Include names, addresses, silence and a caller interrupting a long answer.
Save a known working configuration and move one test route first. Inspect the call log before increasing traffic. Follow the staged migration guide.
Understand the bill
APIFleet adds $0.03 per connected AI minute, billed per second. Provider and carrier usage are additional. With your own keys, provider charges go directly to the provider. No monthly subscription or free call credits; prepaid top-ups start at $10.