Retell AI

✓ Editorially verified

Build, test and deploy production-grade AI voice agents for inbound and outbound calls.

Freemium· Free $10 starter credit. Pay-as-you-go voice agents ~$0.07-$0.31/min (Retell voice infra $0.055/min + TTS ~$0.015/min + LLM $0.003-$0.32/min + telephony). Chat agents $0.001-$0.052/message. Add-ons: knowledge base $0.005/min or $8/mo, denoising $0.005/min, PII removal $0.01/min, AI QA $0.10/min, batch call $0.005/dial, SMS $0.01/msg. Phone numbers $2/mo, extra concurrency $8/mo, verified number $10/mo. Enterprise: custom.AudioLLM-agnostic (OpenAI, Anthropic, Google and others selectable per agent); proprietary turn-taking model and voice pipeline in-house

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Best for

Product and CX teams building production voice agents for high-volume inbound support or outbound sales — especially in healthcare, insurance, financial services and logistics where compliance, low latency and CRM/telephony integrations matter.

Skip if

Hobbyists prototyping a text-only chatbot, teams that need fully self-hosted or open-source voice stacks, or low-volume use cases where per-minute pricing outweighs the convenience of a managed platform.

Retell AI is a voice-agent platform for building conversational AI that answers and places phone calls at contact-center scale. It stitches together the pieces you would otherwise wire up yourself — speech-to-text, LLM orchestration, low-latency text-to-speech, telephony (or bring-your-own via Twilio, Vonage, Telnyx, Amazon Connect, Genesys, Five9, Avaya), and a turn-taking model tuned for natural back-and-forth — behind a single API and no-code dashboard. Advertised end-to-end latency is around 600 ms, which is the threshold at which callers stop noticing the pause.

Agents are configured with a system prompt, a knowledge base (streaming RAG with auto-sync), and function-call tools that let the model book appointments, transfer to a human, look up an order, take payment or push data into HubSpot, Salesforce, Cal.com, n8n, Zapier or Make. The product ships with the operational scaffolding voice deployments actually need: call recording and transcripts, simulation-based regression testing against personas, continuous QA scoring, PII redaction, safety guardrails, denoising and branded caller ID. Compliance covers HIPAA, SOC 2 Type II and GDPR, which is why the case studies skew healthcare, insurance, financial services and logistics.

Typical workflows are outbound campaigns (lead qualification, appointment reminders, collections dialers with batch-call), 24/7 inbound triage and IVR replacement, and chat/SMS agents that share the same knowledge base and tools as the voice bot. Teams generally prototype in the dashboard, then move to the API or SDK for production, and pay per minute plus per add-on rather than a flat seat licence.

Editor's take

Retell is the pragmatic default if you actually want to ship a voice agent this quarter rather than reinvent STT-LLM-TTS plumbing. The latency is real, the QA and simulation tooling is what separates a demo from production, and the telephony integrations save weeks. Just model your per-minute economics honestly before you turn on every add-on — the sticker price grows fast.

— The AI Tool Bible editorial team

Pros

✅ Sub-second end-to-end latency (~600 ms) with a purpose-built turn-taking model — conversations feel natural rather than walkie-talkie.
✅ Batteries-included telephony: bring Twilio/Vonage/Telnyx/Amazon Connect or use Retell-provisioned numbers with SIP trunking.
✅ Real function calling for booking, transfers, payments and CRM writes, with pre-built HubSpot, Salesforce, Cal.com, n8n, Zapier and Make integrations.
✅ Streaming RAG knowledge base with auto-sync, plus simulation testing and continuous QA — the operational glue most DIY voice stacks skip.
✅ Enterprise compliance out of the box: HIPAA, SOC 2 Type II, GDPR, PII removal and safety guardrails as toggleable add-ons.
✅ Genuinely transparent pay-as-you-go pricing with a $10 starter credit, so you can benchmark cost per call before committing.

Cons

⚠️ Per-minute costs stack quickly once you enable QA ($0.10/min), knowledge base, denoising and premium LLMs — a 'cheap' agent can land near $0.30+/min.
⚠️ The specific LLMs are pluggable but Retell doesn't publish a default recommendation, so cost/quality tuning is on you.
⚠️ Not open source and there is no self-hosted option — regulated buyers who need on-prem inference are out of scope.
⚠️ Voice/telephony focus means it is overkill (and overpriced) for pure text chatbots you could run on a generic LLM API.
⚠️ True enterprise features (unlimited concurrency, custom compliance, dedicated support) require a sales conversation, not a self-serve upgrade.

Use cases

AI inbound call answeringOutbound lead qualificationAppointment scheduling and remindersCollections and payment dialers24/7 customer support triageIVR replacementHealthcare intake and follow-up callsInsurance claims first-notice-of-lossVoice-enabled RAG knowledge assistantsChat and SMS agents sharing a voice knowledge base