Built by Retell AI for businesses automating inbound and outbound phone call handling.

Provides speech recognition, LLM reasoning, and text-to-speech orchestration for low-latency phone voice agents.

Delivered as a hosted platform integrated with telephony providers and CRMs like Salesforce and HubSpot.

Launched around 2023 and reports powering tens of millions of monthly calls by late 2025.

Automates call center tasks like scheduling, lead qualification, and customer service at scale.

Depends on underlying speech and language models plus telephony carriers for call delivery.

Commercial hosted service, closed source, call audio and transcripts are processed on Retell's cloud infrastructure.