When creating a tool with type: "transfer_call" via the Create Tool endpoint, the static_params object configures how calls are transferred — including routing, transfer type, and warm transfer behavior.
When creating a transfer_call tool, the following tool-level fields should be set alongside your static_params:
| Field | Recommended Value | Notes |
|---|
speak_during_execution | false | AI should not speak during the transfer. The dashboard sets this to false. If omitted, the database default is true. |
speak_after_execution | false | AI should not speak after the transfer. The dashboard sets this to false. If omitted, the database default is true. |
async | false | The dashboard sets this to false. Defaults to false if omitted. |
If you omit speak_during_execution and speak_after_execution, they will default to true (the database default), which is not the intended behavior for transfer calls. Always set them explicitly to false.
Basic Fields
These fields are at the top level of static_params:
| Field | Type | Required | Description |
|---|
routing_rules | string | Conditional | Dynamic routing logic that tells the AI where to transfer based on conversation context. Must include phone numbers with country codes. Required if default_transfer_number is not set. |
default_transfer_number | string | Conditional | A fixed phone number in E.164 format (e.g., +15551234567) to transfer all calls to. Required if routing_rules is not set. |
transfer_type | "cold" | "warm" | Yes | "cold": the call is transferred immediately without a debrief. "warm": the AI provides context to the receiving agent before connecting the caller. |
You must provide either routing_rules or default_transfer_number (or both). When both are set, routing_rules takes precedence and default_transfer_number serves as a fallback.
Warm Transfer Behavior Settings (transfer_settings)
When transfer_type is "warm", include a transfer_settings object inside static_params to configure the handoff behavior. All fields within use snake_case.
Hold & Ring
| Field | Type | Default | Description |
|---|
extension | string | — | Extension number to dial after connecting. Only applicable when using a static number. |
on_hold_music | "ringtone" | "silence" | "music" | "ringtone" | Audio played to the original caller while they wait during the transfer. |
ring_duration | number | 30 | How long (in seconds) to ring the transfer destination before giving up. Min: 10, Max: 120. |
IVR Navigation
| Field | Type | Default | Description |
|---|
navigate_ivr | boolean | false | Enable this if the transfer destination has an IVR (automated phone menu) that needs to be navigated. |
navigate_ivr_prompt | string | — | Instructions for the AI on how to navigate the IVR. Only used when navigate_ivr is true. Example: "Navigate to the sales department by pressing 2". |
Human Detection
| Field | Type | Default | Description |
|---|
human_detection | boolean | false | When enabled, the AI will only proceed with the debrief if it detects a real human (not a voicemail or automated system). |
detection_timeout | number | 30 | Maximum seconds the AI waits to determine if the transfer target is a human. Min: 0, Max: 300. Only used when human_detection is true. |
ai_auto_greet | boolean | true | When enabled, the AI says “Hello” after connecting to encourage a response from the transfer target. Only used when human_detection is true. |
Whisper Message
A private message spoken only to the transfer target (receiving agent) before connecting them to the original caller.
| Field | Type | Default | Description |
|---|
whisper_message | boolean | true | Whether to speak a whisper message to the transfer target. |
whisper_message_type | "prompt" | "static" | — | How the whisper message is generated. Only used when whisper_message is true. |
whisper_message_prompt | string | "Give the User a brief summary like name of the caller, purpose etc" | AI prompt to generate the whisper message dynamically. Used when whisper_message_type is "prompt". |
whisper_message_static | string | — | A fixed whisper message. Used when whisper_message_type is "static". |
Human Agent Confirmation
| Field | Type | Default | Description |
|---|
human_confirmation | boolean | true | When enabled, the AI asks the receiving agent for confirmation before connecting the original caller. If the agent declines, the transfer is cancelled. |
Check Availability Message
A message spoken to the original caller while the AI checks if the transfer target is available.
| Field | Type | Default | Description |
|---|
check_availability_message | boolean | true | Whether to speak a message while checking availability. |
check_availability_message_type | "prompt" | "static" | — | How the message is generated. Only used when check_availability_message is true. |
check_availability_message_prompt | string | "Say please hold on, I will check if they are available" | AI prompt for generating the message. Used when type is "prompt". |
check_availability_message_static | string | — | A fixed message. Used when type is "static". |
Transfer Success Message
A message spoken to the original caller when they are about to be connected to the transfer target.
| Field | Type | Default | Description |
|---|
transfer_success_message | boolean | true | Whether to speak a message when connecting. |
transfer_success_message_type | "prompt" | "static" | — | How the message is generated. Only used when transfer_success_message is true. |
transfer_success_message_prompt | string | "Say like I am transferring you now" | AI prompt for generating the message. Used when type is "prompt". |
transfer_success_message_static | string | — | A fixed message. Used when type is "static". |
Three-Way Message
A message spoken after the transfer is successful, audible to both the original caller and the transfer target.
| Field | Type | Default | Description |
|---|
three_way_message | boolean | false | Whether to speak a three-way message after connecting both parties. |
three_way_message_type | "prompt" | "static" | — | How the message is generated. Only used when three_way_message is true. |
three_way_message_prompt | string | — | AI prompt for generating the message. Example: "Say you both are now connected. I'll be disconnecting now." |
three_way_message_static | string | — | A fixed message. Used when type is "static". |
Fallback Message
A message spoken to the original caller when the transfer target hangs up or doesn’t answer.
| Field | Type | Default | Description |
|---|
fallback_message | boolean | true | Whether to speak a fallback message. |
fallback_message_type | "prompt" | "static" | — | How the message is generated. Only used when fallback_message is true. |
fallback_message_prompt | string | "Say they are not available, I will take a message if you like" | AI prompt for generating the message. Used when type is "prompt". |
fallback_message_static | string | — | A fixed message. Used when type is "static". |
Session Limits
| Field | Type | Default | Description |
|---|
disable_extended_prompt | boolean | false | Prevents the AI from using extended prompting during the warm transfer process. |
max_session_duration_after_transfer | number | 15 | Maximum duration (in minutes) for the call after the transfer completes. Min: 1, Max: 60. |
Webhook Fields
These fields are at the top level of static_params and configure webhook-based dynamic routing as an alternative to static routing.
| Field | Type | Default | Description |
|---|
transfer_number | string | — | Phone number in E.164 format used for webhook mode transfers. |
pre_tool_webhook | boolean | false | When enabled, a webhook is called before executing the transfer. The webhook can return dynamic variables including transfer_number to override the destination. |
pre_tool_webhook_use_pre_call_url | boolean | false | When true, reuses the bot’s pre-call webhook URL instead of a custom URL. |
pre_tool_webhook_url | string | — | Custom webhook URL (must be HTTPS). Used when pre_tool_webhook is true and pre_tool_webhook_use_pre_call_url is false. |
Examples
Cold Transfer to a Static Number
Immediately transfer the call without any debrief.
{
"type": "transfer_call",
"name": "transfer_to_support",
"description": "Transfer the call to the support team when the customer has a technical issue",
"static_params": {
"default_transfer_number": "+15551234567",
"transfer_type": "cold"
},
"speak_during_execution": false,
"speak_after_execution": false,
"async": false
}
Cold Transfer with Dynamic Routing
Route calls to different numbers based on conversation context.
{
"type": "transfer_call",
"name": "transfer_to_department",
"description": "Transfer the call to the appropriate department based on the customer's needs",
"static_params": {
"routing_rules": "If the customer wants support, transfer to +15551234567. If the customer wants sales, transfer to +15559876543. Otherwise, transfer to +15550001111.",
"default_transfer_number": "+15550001111",
"transfer_type": "cold"
},
"speak_during_execution": false,
"speak_after_execution": false,
"async": false
}
Warm Transfer with Debrief
Transfer the call with full warm transfer behavior — whisper message, human detection, and fallback.
{
"type": "transfer_call",
"name": "warm_transfer_to_sales",
"description": "Transfer the call to the sales team with a debrief when the customer wants to make a purchase",
"static_params": {
"default_transfer_number": "+15551234567",
"transfer_type": "warm",
"transfer_settings": {
"on_hold_music": "music",
"ring_duration": 45,
"human_detection": true,
"detection_timeout": 30,
"ai_auto_greet": true,
"whisper_message": true,
"whisper_message_type": "prompt",
"whisper_message_prompt": "Give the agent a brief summary including the caller's name, what they're interested in purchasing, and any relevant details from the conversation.",
"human_confirmation": true,
"check_availability_message": true,
"check_availability_message_type": "prompt",
"check_availability_message_prompt": "Say please hold on, I will check if a sales representative is available.",
"transfer_success_message": true,
"transfer_success_message_type": "static",
"transfer_success_message_static": "I'm connecting you with our sales team now.",
"three_way_message": true,
"three_way_message_type": "static",
"three_way_message_static": "You are both now connected. I'll disconnect now. Thank you!",
"fallback_message": true,
"fallback_message_type": "prompt",
"fallback_message_prompt": "Say that the sales team is not available right now and offer to take a message or schedule a callback.",
"max_session_duration_after_transfer": 30
}
},
"speak_during_execution": false,
"speak_after_execution": false,
"async": false
}
Warm Transfer with IVR Navigation
Transfer to a destination that has an automated phone menu.
{
"type": "transfer_call",
"name": "transfer_to_partner",
"description": "Transfer the call to a partner company's support line",
"static_params": {
"default_transfer_number": "+15559876543",
"transfer_type": "warm",
"transfer_settings": {
"navigate_ivr": true,
"navigate_ivr_prompt": "Navigate to the sales department by pressing 2, then press 1 for English.",
"human_detection": true,
"detection_timeout": 60,
"whisper_message": true,
"whisper_message_type": "static",
"whisper_message_static": "Incoming transfer from OpenMic AI. Customer needs help with their account."
}
},
"speak_during_execution": false,
"speak_after_execution": false,
"async": false
}
Webhook-Based Dynamic Routing
Use a webhook to determine the transfer destination at runtime.
{
"type": "transfer_call",
"name": "dynamic_transfer",
"description": "Transfer the call using dynamic routing based on agent availability",
"static_params": {
"transfer_number": "+15550001111",
"pre_tool_webhook": true,
"pre_tool_webhook_url": "https://your-domain.com/webhook/route-call"
},
"speak_during_execution": false,
"speak_after_execution": false,
"async": false
}
When pre_tool_webhook is enabled, your webhook receives call details and can return a transfer_number in the dynamic_variables response object to override the destination. If the webhook fails or times out (3 seconds), the transfer_number configured in static_params is used as a fallback. See the Pre-Tool Webhook documentation for the request/response format. 
