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In some regions, automated text messages without consent may violate local regulations. You are responsible for ensuring compliance with all relevant laws.
Outbound SMS lets your agent start a text conversation programmatically. You can use this to send a first message for things like welcome texts, appointment reminders, or follow-ups, triggered from tools like Zapier or your own backend scripts. The recipient’s reply is handled as inbound SMS and continues the same conversation. Outbound SMS is supported for Twilio numbers that are assigned for SMS. The number you send from must already be connected and assigned to an environment for SMS.

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Starting an outbound conversation

To start an outbound conversation, send a POST request to your agent’s outbound SMS endpoint. You can find this endpoint by opening Phone numbers in the sidebar, then clicking View in the Outbound SMS API column for your number. The modal displays a ready-to-use curl command with your agent’s endpoint and required headers. You can also test the message directly from this modal by entering a phone number and clicking Send. Each request starts a fresh conversation. Your agent writes the first message from its launch path. You do not supply the message body in the request.

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API reference

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Endpoint

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Headers

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Request body

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Response

A successful request returns 202 with the new session ID. The first text is sent after the request returns, once the agent has run its launch path.
The request is refused if the number is not assigned for SMS, the recipient number is invalid, or the recipient is already in an active turn or a live agent handoff (409). Outbound SMS is also rate limited per recipient and per phone number. The recipient’s phone number is set as the user_id variable, the same way inbound SMS uses the sender’s number.