Retell AI

Overview

Retell AI is a platform for building, testing and running AI voice and chat agents, with telephony built in. Chat agents can hold two-way SMS conversations on a Twilio number, run in a website widget, or connect to your own channel through the chat API. Voice agents can also send texts mid-call. SMS covers US numbers only (no toll-free) and needs an approved A2P 10DLC campaign.

Key features

• Two-way SMS chat agents, plus an outbound SMS API that opens a conversation
• Send SMS during calls, and receive texts and MMS mid-call
• Contact memory shared across calls and SMS chats
• Signed webhooks, a REST API with SDKs, MCP tools and a custom LLM WebSocket
• HIPAA, GDPR, SOC 2 Type 1 and 2 and ISO 27001 listed

Pricing

Pay as you go with $10 in free credit: $0.07 to $0.31 a minute for voice agents and from $0.002 a message for chat agents. The SMS add-on is $20 a month per number plus $0.01 per SMS sent, after one-time registration fees.

How it compares to Linq

Retell texts over SMS only, with no iMessage and no RCS, and has no WhatsApp integration. Linq sends iMessage, RCS and SMS but its API does not place or answer calls, which is Retell's core product. Retell bills per minute and per message; Linq Pro is a flat fee from $260 a month with no per-message fees.

Best for

Developers building AI phone agents in the US that also need to hold SMS conversations.

Sources

• retellai.com
• retellai.com/pricing
• docs.retellai.com/llms.txt
• docs.retellai.com/deploy/enable-sms.md
• docs.retellai.com/build/create-chat-agent.md
• docs.retellai.com/api-references/create-sms-chat.md
• docs.retellai.com/features/inbound-call-webhook.md
• docs.retellai.com/features/contact-memory.md
• docs.retellai.com/general/compliance.md