Documentation Index
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The Transfer Call tool allows your AI agent to hand off an active call to a human agent, department, or any phone number — at exactly the right moment in a conversation. It supports both Cold Transfer (instant handoff) and Warm Transfer (assisted handoff with context sharing) to give you full control over how the transition happens.
Phone calls only. This tool works exclusively for phone calls and is not supported for web-based chat or voice sessions.
When to Use
Trigger this tool when:
- The customer asks to speak with a human agent
- The request requires human judgement or specialist knowledge
- The conversation needs escalation (e.g., complaint, complex query)
- Routing to a specific department is required — Sales, Support, Billing, Renewals, Claims
Steps to Add
- Open the Agent Builder
- Click + Add Tool
- Select Voice Tool Call
- From the Select Action dropdown, choose
voice_transfer_call
- Fill in all configuration fields (described below)
- Click Add to Agent
Write a clear instruction that tells the AI agent when to trigger the transfer. The more specific you are, the more reliably the agent will initiate the transfer at the correct moment.
Transfer the call when the customer asks to speak with a human, expresses frustration,
or needs assistance that goes beyond what the AI can handle.
Transfer to the billing department when the customer raises a payment dispute
or questions their invoice amount.
Step 2: Transfer To
Defines where the call will be sent.
Destination Options
| Option | Description |
|---|
| Static Destination | A fixed phone number or SIP URI — always routes to the same endpoint |
| Dynamic Routing | Destination is resolved at runtime from a {{variable_name}} extracted during the conversation |
- Phone number (E.164 format):
+919876543210
- SIP URI:
sip:agent@yourdomain.com
- Dynamic variable:
{{assigned_agent_number}}
All phone numbers must be in E.164 international format, including the country code (e.g., +1 for US, +91 for India).
Extension Number (Optional)
After the main number connects, the extension routes the call to the correct internal team or agent — automatically, without the customer needing to press anything.
Main Number: +1-800-555-0199 ← connects to the company switchboard
Extension: 302 ← routes directly to the Billing team
Why the Extension Field Matters
Most business phone systems (PBX, RingCentral, 8x8, Vonage, Twilio) share a single main inbound number across departments. Without an extension, the AI agent connects to the front-line IVR or receptionist and stalls — requiring manual routing.
With the extension configured, the handoff is seamless: the agent dials the main number and immediately routes to the right desk, with no customer interaction needed.
When to Use the Extension
Your business has multiple departments on one main line:
Main: +1-888-200-1000
├── ext. 101 → Sales
├── ext. 202 → Customer Support
└── ext. 303 → Billing & Accounts
Static vs. Dynamic Extension
Static — same extension on every transfer:
Best for single-purpose bots where all transfers always go to one team.
Dynamic — extension resolved from conversation context:
Extension: {{department_extension}}
| Customer Says | Extracted Intent | Extension Routed |
|---|
| ”I want to renew my policy” | renewals | 201 |
| ”I need to file a claim” | claims | 305 |
| ”I have a billing question” | billing | 410 |
| ”I want to cancel” | cancellations | 500 |
Step 3: Transfer Type
SigmaMind provides two transfer types. Choose based on whether context sharing is needed before the customer connects.
Cold Transfer
The AI agent immediately routes the call to the destination and disconnects.
What happens:
- The AI initiates the transfer and exits the conversation instantly
- The customer hears ringing and connects directly to the destination
- No context or summary is shared with the receiving agent
When to use Cold Transfer:
- Simple department routing where no background is needed
- Fast escalations where speed matters more than context
- Internal lines where agents already have CRM access
Customer: "Can I speak to someone in support?"
→ AI triggers voice_transfer_call
→ Call routes to +1-800-555-0100
→ AI drops off immediately
→ Customer hears ringing, support agent picks up
Warm Transfer
The receiving agent is connected first, context is shared privately, then the customer is bridged in. This creates a smooth, professional handoff experience.
Warm Transfer happens in two distinct stages:
Stage 1: Connecting Stage
In the Connecting Stage, the receiving agent’s line is dialed and connected — but the customer and the agent cannot yet hear each other. The customer is still on hold, listening to ringing or hold music.
This stage exists so the receiving agent can receive context before the customer joins, allowing them to prepare a response or pull up the right information.
[Connecting Stage]
Customer ──── on hold (hears ringing) ────►
AI ──► Agent connected
↓
Whisper Message played to agent only
Whisper Message
The Whisper Message is a private audio message played only to the receiving agent during the Connecting Stage. The customer cannot hear it under any circumstances.
Use the Whisper Message to give the agent the context they need before they say hello — customer name, reason for calling, policy number, account history, or any other relevant detail.
To enable Whisper Message:
- Toggle Whisper Message ON
- Enter your message in the text box
- Choose either Static or Prompt mode
Static Whisper Message
A fixed, pre-written message — the same text plays on every transfer.
You are being connected to a customer regarding an insurance renewal request.
Please review their policy and assist accordingly.
You are being connected to {{customer_name}} regarding insurance policy {{policy_id}}.
The customer wants assistance with {{request_type}}.
Please have their account ready before greeting them.
Prompt Whisper Message
Instead of writing a fixed message, you provide an instruction — and SigmaMind AI automatically generates a contextual summary based on the actual conversation before playing it to the agent.
Prompt instruction:
Summarize the customer's request and include their name, issue, and requested service.
Customer name is Rahul Sharma. He is calling to renew his car insurance policy
and wants clarification on premium pricing and coverage details.
Provide a short summary for the receiving agent. Include customer name {{customer_name}},
service {{service_type}}, and request {{customer_request}}.
If the Whisper Message is left empty, the transfer will still proceed, but no context will be shared with the receiving agent. In this case, the Warm Transfer effectively behaves like a Cold Transfer.
Stage 2: Bridged Stage
In the Bridged Stage, the call bridge is established and both the customer and the receiving agent can now hear each other. The AI agent drops off, and the human takes over the conversation.
This is the moment the transfer is truly complete.
[Bridged Stage]
Customer ◄──────────────────────────► Human Agent
(full duplex audio)
AI drops off
Three-Way Message (Bridge Message)
At the moment of bridging, the AI can play one final message heard by both the customer and the receiving agent simultaneously. This ensures a clear, professional transition and eliminates any awkward silence or confusion about whether the connection has succeeded.
To enable Three-Way Message:
- Toggle Three-way Message ON
- Enter the message in the text box
- Choose either Static or Prompt mode
Static Three-Way Message
A fixed announcement confirming the connection:
Thank you for waiting. You are now connected to our support specialist.
Thank you for waiting, {{customer_name}}. You are now connected to our support specialist.
Prompt Three-Way Message
A dynamically generated message tailored to the specific call:
Generate a short, clear, and neutral three-way message to be played to both the customer
and the agent after the call is bridged. Confirm the connection is complete and invite
the conversation to continue. Keep it professional and concise.
Generate a short, clear, and neutral three-way message to be played to both {{customer_name}}
and the agent after the call is bridged. Mention that {{customer_name}} is now connected
with the {{agent_role}} regarding {{call_reason}}.
Keep it professional, concise, and welcoming.
All variables must always be written using double curly braces: {{variable_name}}
Custom Headers let you send structured metadata along with the call transfer. This information is invisible to the customer but available to the receiving agent’s system, CRM, call center software, or backend automation.
Headers are sent as key-value pairs:
X-Intent: billing_issue
X-Language: en
X-Customer-Type: existing
X-Ticket-ID: 12345
X-Call-Source: outbound_campaign
X-Policy-ID: POL-98271
| Use Case | Header Example |
|---|
| Route to the right CRM queue | X-Intent: claims_inquiry |
| Tag language for multilingual teams | X-Language: hi |
| Associate call with a campaign | X-Call-Source: renewal_campaign_Q2 |
| Pre-load customer record | X-Customer-ID: CUS-00421 |
| Log call reason for reporting | X-Call-Reason: cancellation_request |
Step 5: Add to Agent
Once all fields are configured, click Add to Agent to save the tool.
If the receiving agent does not answer or the transfer fails due to network issues, SigmaMind automatically retries the transfer based on your configured settings.
Full Warm Transfer Execution Flow
Customer requests transfer
↓
AI triggers voice_transfer_call
↓
[Connecting Stage]
Receiving agent's line is dialed
Customer placed on hold (hears ringing)
↓
Whisper Message played to agent only
(Customer cannot hear this)
↓
[Bridged Stage]
Call bridge established
Both customer and agent can hear each other
↓
Three-way Message played to both parties
↓
AI drops off
Human agent continues the conversation
Cold vs. Warm
| Feature | Cold Transfer | Warm Transfer |
|---|
| Agent connected before customer | ❌ | ✅ |
| Whisper Message to receiving agent | ❌ | ✅ |
| Three-way bridge announcement | ❌ | ✅ |
| Customer hears hold music | ❌ | ✅ |
| Context shared before handoff | ❌ | ✅ |
| Speed | Fastest | Slightly slower (seconds) |
| Best for | Simple routing | High-stakes or complex calls |
Example Configurations
Example 1 — Cold Transfer to Support
| Field | Value |
|---|
| Instruction | Transfer when the customer requests a human agent. |
| Transfer To | Static → +1-800-555-0100 |
| Extension | 202 |
| Transfer Type | Cold Transfer |
Example 2 — Warm Transfer with Whisper + Bridge Message
| Field | Value |
|---|
| Instruction | Transfer when the customer raises a billing dispute or payment issue. |
| Transfer To | Static → +1-800-555-0199 |
| Extension | {{department_extension}} |
| Transfer Type | Warm Transfer |
| Whisper Message | You are being connected to {{customer_name}} regarding a billing dispute on policy {{policy_id}}. |
| Three-way Message | Thank you for waiting, {{customer_name}}. You are now connected with our billing specialist. |
Best Practices
- Write specific trigger instructions — vague conditions cause missed or premature transfers
- Use Warm Transfer for high-value calls, complaints, or any scenario where the receiving agent benefits from knowing context upfront
- Use Prompt Whisper Messages when call topics vary widely — the AI generates a tailored summary every time
- Pair Dynamic Routing with Extract Dynamic Variables to handle multi-department routing from a single transfer tool
- Use Custom Headers to pre-load CRM records or tag calls for analytics — reduces repeat questions for the customer
- Always enter phone numbers in E.164 format (
+[country code][number])
- Test transfer flows using the Test Voice playground before going live
Troubleshooting
| Issue | Fix |
|---|
| Transfer not triggering | Make the Instruction more specific and match actual conversation phrases |
| Call drops instead of transferring | Verify phone number is in correct E.164 format |
| Extension not connecting | Confirm the extension is active on your PBX/phone system and accepts auto-dial |
| Dynamic variable not resolving | Ensure Extract Dynamic Variables runs earlier in the agent flow |
| Whisper message not playing | Check that the Whisper Message toggle is ON and the message text is not empty |
| Warm transfer behaves like cold | Whisper Message is likely empty — add content to distinguish the stages |
| Three-way message not heard | Confirm the Three-way Message toggle is ON in the Bridged Stage settings |
