We’d like to implement automatic follow-up messages for outbound SMS chats when a customer has not replied after a set period.
Currently, /create-chat-completion can add/generated messages in the chat, but those messages do not appear to be delivered over SMS. Is there any supported way to make /create-chat-completion send the generated message through the existing SMS chat transport?
If not, could Retell add native auto follow-ups for outbound SMS chats, or provide an API endpoint to send an agent-generated SMS message into an existing sms_chat conversation?
Hello @george1 The /create-chat-completion endpoint does not send messages over SMS. It generates agent responses within the chat session’s message history, but it does not send those messages through the SMS transport of an existing sms_chat conversation.
The supported method for sending an outbound SMS is POST /create-sms-chat, which starts a new conversation and sends an initial agent-generated message. It cannot resume or send follow-up messages within an existing SMS conversation.
For your use case of sending timed follow-ups on an existing conversation, this functionality is not currently supported. If this would be useful for your workflow, please submit it as a feature request in the Feature Requests section of the forum for the team to review.
Hey @george1 Confirming your read: /create-chat-completion is the completion endpoint for text-chat (custom-UI) sessions. It generates and persists the next agent turn but doesn’t run the Twilio dispatch path, so calling it against an sms_chat won’t deliver over SMS. There’s no supported flag today to bridge it, and we don’t have a native “auto follow-up on silence” scheduler.
Workaround - orchestrate follow-ups from your side using /create-sms-chat:
That endpoint creates the chat and sends the first outbound SMS in one call.
Track silence using the chat webhooks - timer/cron per open chat.
When the window elapses, close the original with POST /end-chat (keeps inbound routing clean).
Fire the follow-up with POST /create-sms-chat:
Same Retell from-number, same recipient
override_agent_id if you want a dedicated follow-up agent
Carry context via retell_llm_dynamic_variables (fetch prior transcript with GET /get-chat/{chat_id} and pass a summary, e.g. {“prior_transcript”: “…”} referenced in the prompt) - new chats are cold-start, they don’t inherit history
Ensure the agent has a Begin Message with startSpeaker=agent OR pass the opening text in the payload, otherwise the chat is created but silent
I’ll also log two feature requests on your behalf: (a) native auto follow-up on silence for sms_chat, and (b) an API to send an agent-generated message into an existing sms_chat.