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When creating a tool with type: "send_sms" via the Create Tool endpoint, the static_params object configures how the SMS message is generated and sent.
When creating a send_sms tool, the following tool-level fields are recommended alongside your static_params:
FieldRecommended ValueNotes
speak_during_executiontrueAI speaks to the caller while the SMS is being sent. Defaults to true if omitted.
speak_after_executiontrueAI speaks to the caller after the SMS is sent. Defaults to true if omitted.
asyncfalseDefaults to false if omitted.

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Static Params Schema

FieldTypeRequiredDescription
type"prompt" | "static"YesDetermines how the SMS message is generated. "prompt" uses AI to compose the message dynamically; "static" sends a fixed, pre-written message.
messagestringYesThe content of the SMS. When type is "static", this is the exact message sent. When type is "prompt", this is an instruction the AI uses to generate the message based on conversation context.

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Examples

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Static Message

Send the same fixed message every time the tool is triggered. 
{
  "type": "send_sms",
  "name": "send_confirmation_sms",
  "description": "Send appointment confirmation via SMS when the customer books an appointment",
  "static_params": {
    "type": "static",
    "message": "Your appointment has been confirmed for {{appointment_date}} at {{appointment_time}}. Reply CANCEL to cancel."
  },
  "speak_during_execution": true,
  "speak_after_execution": true
}

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AI-Generated Message (Prompt)

Let the AI compose the SMS dynamically based on the conversation context. 
{
  "type": "send_sms",
  "name": "send_followup_sms",
  "description": "Send a follow-up SMS with the information the customer requested during the call",
  "static_params": {
    "type": "prompt",
    "message": "Generate an SMS summarizing the key points discussed in this conversation, including any action items or next steps."
  },
  "speak_during_execution": true,
  "speak_after_execution": true
}

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Dynamic Variables

When using type: "static", you can include dynamic variables in the message using double curly braces. These variables are resolved at runtime from the conversation context or tool parameters. 
Your order #{{order_id}} has been confirmed. Estimated delivery: {{delivery_date}}.
For the UI-based setup guide, see the Send SMS Custom Function documentation.