Retell AI

What it does

Writes tests

PartlyProduces graded conversation test cases for its own agents, not software tests.Run graded test cases to catch regressions before launch.docs.retellai.com/general/introduction ↗

Done-for-you service

PartlyYou run the software self-serve; Retell sells dedicated implementation support as an Enterprise add-on rather than a managed service, and points elsewhere to certified partners.Dedicated Implementation Support (add-on)retellai.com/pricing ↗

How much it does unattended

Runs autonomously

YesAgents run whole calls unattended: answering, qualifying, booking and updating systems. Escalation to a person happens only when the conversation needs one.An AI voice agent is an autonomous system that can listen, speak, and hold natural phone conversations like a human.retellai.com ↗

Multi-agent

YesAgent Transfer (agent swap) hands a live call from one AI agent to another with full transcript inherited; subagent nodes attach tool-using agents inside a flow.Agent Transfer (also known as Agent Swap) enables you to modularize tasks and re-use specialized agentsdocs.retellai.com/build/conversation-fl… ↗

Agent permissions

PartlyThe agent completes calls without asking, but a human can monitor live and seize the call, and guardrails plus PII removal are configurable metered add-ons.Step in whenever you need to. Monitor AI calls live, listen in, and take over the conversation instantly when a human touch is needed.retellai.com ↗

Which models it runs on

Claude

YesClaude Sonnet and Haiku models are selectable for voice agents, priced per minute, and for chat agents per AI message.Claude 4.5 sonnetretellai.com/pricing ↗

GPT

YesGPT models dominate the model menu, with both the standard STT-LLM-TTS path and GPT Realtime speech-to-speech priced per minute.GPT 5.2retellai.com/pricing ↗

Open models

PartlyThe hosted model menu enumerates only OpenAI, Anthropic and Google models, so no open-weight model is offered, but the custom LLM WebSocket path exists precisely so you can host one yourself.A fine-tuned model, a self-hosted open-weights model, or a provider outside the supported options.docs.retellai.com/integrate-llm/overview ↗

Model choice

YesYou pick the LLM per agent from a published menu of 20+ models, each with its own per-minute rate, plus a fast tier and a custom-LLM escape hatch.Set up a Retell single or multi-prompt agent: choose the language model, pick a voice and speaking speed, and decide who speaks first on the call.docs.retellai.com/build/single-multi-pr… ↗

Where you use it

In your editor

PartlyRetell's own MCP server lets Cursor, Claude Desktop, Claude Code and Codex-style clients create, publish and inspect agents; the agent itself never runs in an editor.Retell supports the Model Context Protocol (MCP) so you can build Retell AI voice agents directly from MCP-capable clients (Cursor, Claude Desktop,…docs.retellai.com/get-started/mcp-server ↗

On the command line

NoThe docs enumerate every way to drive Retell: dashboard, REST API, Node/Python SDKs and MCP server. No command-line tool is among them.Build entirely from the dashboard with no code, or go fully programmatic with the API, SDKs, and an MCP server.docs.retellai.com/general/introduction ↗

In a browser

YesEverything is built and run from the hosted dashboard, and agents themselves deploy to a website voice or chat widget and browser web calls.Deploy your agent in minutes for inbound calls, outbound campaigns, web, or SMS. Connect phone numbers, launch an outbound dialer, or embed a website…retellai.com ↗

Whose machine it runs on

Self-hosted

PartlyOn-prem deployment is an Enterprise offering; on pay-as-you-go the only self-hosted piece is your own LLM behind the custom-LLM WebSocket, or your own SIP telephony.Deploy Retell within your own infrastructure to meet strict security and data residency requirements.retellai.com ↗

Not established: Open source

What it costs to run

How it meters

YesMetered per minute of voice, split into Retell voice infra ($0.055/min), the chosen LLM, TTS and telephony; chat agents meter per AI message; concurrency, numbers and knowledge bases bill monthly.Usage costs — everything metered, such as per-minute call costs (voice, LLM, telephony) — are deducted from your credit balance in real time.docs.retellai.com/accounts/billing ↗

Free tier

YesSelf-serve signup with $10 of trial credit and full platform access, no call and no card required to start; the credit is granted once per email address.Go live in minutes with $10 in free credits. Full platform access, no commitments. Just build, test, and pay as you scale.retellai.com/pricing ↗

API access

YesREST API at api.retellai.com with bearer API keys, official Node and Python SDKs, and webhooks, all included on pay-as-you-go rather than gated to Enterprise.Use this section to build and manage Retell AI voice and chat agents programmatically.docs.retellai.com/api-references/overvi… ↗

MCP server

YesA hosted MCP server at mcp.retellai.com exposes agents, calls, numbers, knowledge bases, testing and QA as tools over Streamable HTTP with a Retell API key.Runtime: MCP clients connect to a hosted (remote) MCP endpoint over Streamable HTTP, authenticate with your Retell API key, then call tools.docs.retellai.com/get-started/mcp-server ↗

Bring your own key

YesCustom LLM mode gives you response generation on your own server and model; custom telephony over SIP carries no Retell telephony charge, and integration credentials are your own keys.With a custom LLM, you own response generation.docs.retellai.com/integrate-llm/overview ↗

Buying it for a team

A company can buy it

YesWorkspaces are the billing and membership unit, with invited members and roles, and Enterprise is contracted with volume pricing and custom MSA/DPA terms.Purpose-built for organizations that demand higher reliability, tighter compliance, and dedicated support, with volume pricing that scales as you…retellai.com/pricing ↗

Seat model

NoNo seat charge and no seat floor: the Monthly Subscription Items table lists every recurring line item (phone numbers, SMS, concurrency, knowledge bases, verified numbers) and none is a seat. Capacity is bought as concurrent calls at $8 each per month.You pay only for what you consume. No minimums, no contracts, no surprises.retellai.com/pricing ↗

Pooled budget

YesOne prepaid credit balance per workspace funds every member's usage, with auto-recharge thresholds; a second workspace gets its own separate balance and card.Billing is scoped per workspace, not per account. Every workspace, including new ones you create later, has its own payment method, credit balance,…docs.retellai.com/accounts/billing ↗

Admin controls

PartlyRole-based access control is sold as an Enterprise line, marked absent for pay-as-you-go in the plan table, yet the docs describe Admin/Developer/Member roles with no tier restriction; API keys can be scoped read or edit on any plan. Contradiction recorded in notes.retellai.com/pricing ↗

Audit log

PartlyAgent configuration changes are recorded as immutable published versions with browsable history and side-by-side comparison; no workspace-level log of administrative actions such as role changes or key rotation is documented.Version control & history: you can create multiple draft versions from any past version, track your version history, and publish any draft when it's…docs.retellai.com/agent/version ↗

Single sign-on

PartlyCustom SSO is an Enterprise line and the plan table marks SSO absent for pay-as-you-go; every account can instead sign in with Google through Auth0, and the vendor names no specific SAML or OIDC support.retellai.com/pricing ↗

What happens to your code

Opt out of training

NoThe privacy policy lists training its AI models among the uses of collected data, and its 'Your Choices' section offers only account deletion, cookie preferences, marketing opt-out and sale/sharing opt-out, with no training opt-out.to train the artificial intelligence models that support our Services or that support our business and administrative functionsretellai.com/legal/privacy-policy ↗

Data residency

PartlyRetell is US-based and runs on AWS with data primarily stored and processed in the United States, with SCCs for EEA/UK transfers; EU-resident processing is not offered, and on-prem deployment for residency requirements is an Enterprise path.However, please note that we do not currently operate services within the European Union.docs.retellai.com/general/compliance ↗

Getting out

YesFiltered call and chat history exports to CSV including transcripts and recording URLs, and List/Get Call APIs return full records; separately, docs.retellai.com/accounts/billing states prepaid credits never expire but are non-refundable.Completed export records are kept for one week.docs.retellai.com/features/session-hist… ↗

Certifications

YesHIPAA with a self-signable BAA, GDPR with a DPA including EU SCCs, and SOC 2 Type 1 and Type 2, with certificates in a Vanta trust centre; ISO 27001 is claimed on the homepage only.we are proud to be HIPAA compliant, GDPR compliant, SOC 2 Type 1 & Type 2 certifieddocs.retellai.com/general/compliance ↗