Sistava

Retell AI

Developer-friendly voice, chat, and SMS agent builder with ~600ms latency

About Retell AI

Retell AI is a developer-oriented platform for building conversational agents with around 600ms turn-taking latency on voice, which is genuinely best-in-class for the category. It is not voice-only: they sell AI-powered conversations across web and in-app chat, SMS workflows, and an MCP server for managing agents from Cursor or Claude Desktop. Honest concession: on raw voice quality and latency, a tuned Retell agent will beat a generalist platform. Sistava is built for a different shape of buyer: someone who wants a worker whose job continues after the conversation ends, with persistent memory, task boards, file drive, and thousands of app integrations.

Platform details

Official website

What does Retell AI actually do?

Retell AI is a voice agent infrastructure platform that lets developers compose phone agents by mixing language models, voice providers, and telephony, then deploy them with no monthly minimum. The differentiator is component choice: buyers can pair GPT, Claude, or Gemini with voice engines from ElevenLabs, Cartesia, OpenAI, MiniMax, or Retell's own stack, and the per-minute price reflects whatever combination they pick. On top of the runtime, Retell ships built-in call analytics, transcription, simulated test conversations before launch, and the operational controls a real production deployment needs (concurrency, post-call webhooks, function calling). The platform is SOC 2 certified and HIPAA-ready, which is rare at this layer of the stack. It also reaches past the phone. Retell sells AI-powered conversations across web and in-app chat plus SMS workflows, integrates with HubSpot, Salesforce, Go High Level, Twilio, Vonage, Telnyx, Amazon Connect, Avaya, Genesys, Five9, n8n, Make, Zapier and Cal.com, and ships an MCP server so you can manage agents from Cursor or Claude Desktop. Where Retell sits in the market is closer to a conversation-aware LLM gateway than a finished agent. The buyer assembles the agent; Retell handles the audio pipeline, observability, and compliance plumbing. For a workforce-style product like Sistava, that role gets absorbed into a higher-level agent abstraction; for teams who want to choose every component, Retell is the most transparent option.

How much does Retell AI cost?

Retell AI is usage-only with no required monthly subscription. The floor is around $0.07 per minute on the cheapest combination of providers, and the published LLM rows show the spread: GPT 4.1 at $0.045/min, Claude 5 Sonnet at $0.08/min, GPT 5.5 at $0.16/min, so an all-in setup lands roughly between $0.13 and $0.31 per minute. Chat agents are metered separately from $0.002 per message. Every account gets $10 in free credits and 20 concurrent calls included; extra concurrency is $8 per call per month. Because cost is itemized by component, buyers can dial price up or down deliberately. Cheaper voices and smaller LLMs cut the per-minute rate for high-volume support flows; premium voices for outbound sales bring it back up. Add-ons are priced on the same principle: Knowledge Base adds $0.005/min plus $8.00 per knowledge base per month with the first 10 free, PII Removal adds $0.01/min, AI Quality Assurance runs $0.10/min after 100 free minutes, Branded Call adds $0.10 per outbound call, and phone numbers are $2.00/month. Enterprise terms unlock 50+ concurrency and custom compliance. Versus Bland AI's bundled per-minute rate, Retell trades simplicity for granularity. Versus a workforce platform like Sistava that charges in credits rather than minutes, Retell is the right shape when voice is the whole product and the wrong shape when voice is one channel among many. Worth noting: Retell has scaled on that thin $5.1M seed rather than a large war chest, reportedly reaching around $50M in annual recurring revenue in 2025 and landing on Wing VC's Enterprise Tech 30 list for 2026, a sign the usage-based model is working at the revenue level, not just the pricing-page level.

When does Retell AI beat the alternatives?

Retell AI wins when the buyer wants to own the architecture of the voice agent and cares about specific component choices. Picking the exact LLM, the exact voice, and the exact telephony lane is something most platforms hide; Retell exposes it. For teams optimizing latency, accent quality, or per-minute cost down to the last cent, that control is the value. Compliance is the second deciding factor. SOC 2 and HIPAA-readiness, plus the ability to sign custom BAAs at enterprise, make Retell viable for healthcare and financial-services use cases that block most consumer-facing voice tools. The fact that the platform is also $0.07 per minute at the entry point makes it credible for pilots, not just enterprise rollouts. Retell loses when the buyer wants an off-the-shelf employee instead of a runtime. A founder who wants an outbound caller, an email follow-up, and a CRM update without choosing a voice provider or wiring the pieces should look at a workforce product like Sistava, where the components are pre-assembled and the unit of work is a task, not a minute or a message.

Where does Retell AI fall short?

Retell AI is a voice infrastructure product, not a finished agent, and that places the assembly burden on the buyer. Picking the right LLM, the right voice, and the right concurrency tier all need experimentation, and the team needs to be comfortable enough with prompts and webhooks to wire the agent to the rest of their stack. The second gap is scope of job rather than scope of channel. Retell covers voice, chat and SMS well and integrates with the CRM and contact-centre stack. What it does not do is own the work that has no conversation in it: research a prospect before the call, write the follow-up sequence, keep a project moving for a week. Teams wanting that stitch other tools alongside it, which means more vendors and more reconciliation when something breaks. Third is the lack of operational wrapping around the runtime. There is no shared inbox, no work journal, no skill marketplace, no employee onboarding flow. A buyer who wants something that feels like a hired worker rather than an SDK should look at workforce platforms like Sistava, which package the voice runtime inside a broader employee abstraction so the day-to-day experience is task management instead of provider selection.

How does Retell AI handle compliance and scale?

Retell AI is SOC 2 certified and HIPAA-ready out of the box, with single sign-on and the ability to sign custom compliance terms at the enterprise tier. For a voice infrastructure product, that posture is uncommon. Most competitors either skip HIPAA entirely or gate it behind a contract negotiation, so teams in healthcare, finance, and other regulated verticals can pilot Retell with minimal friction. Scale-out follows the same self-serve pattern. Every account starts with 20 concurrent calls, and additional concurrency is $8 per call per month, so a team can grow from a 50-call test to a 500-call rollout without a sales conversation. Enterprise plans push concurrency higher and add dedicated infrastructure. Compliance is necessary but rarely sufficient for buying decisions. Teams that need both regulatory posture and a broader workforce (research, follow-ups, CRM hygiene) often pair Retell with a higher-level agent platform, or pick a workforce product like Sistava that bundles compliance, voice, and the rest of the day into one place.

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