2. In-Call Functions

Purpose: take real-time actions while talking to the customer on the call. Key points:

• They run while the customer is on the call, so they can interact with the customer.
• They are triggered by customer intent.
• They perform actions immediately.
• Their responses should sound natural.
• You can add messages for the agent to say while the action runs.

Common uses: book or reschedule appointments, check availability and pitch slots, send product details or documents over WhatsApp during the call, calculate EMI or discounts or interest rates live, capture exchange details, transfer calls, put calls on hold, update the lead stage, and trigger callbacks. Example: bookTestDrive(name=“Rohit”, slot=“2026-06-15T12:00:00”) returns a booking confirmation or a failure.

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Types of In-Call Functions

• Keep Call on Hold: puts the call on hold; the agent stays silent for that time. Use it as keep_call_on_hold in the system prompt. It needs a Description (when to put the call on hold) and a Hold Duration (how long, in seconds, to stay silent). Use case: if the customer says “2 min dijiye abhi dekh kar batata hu,” then instead of saying a Silence Message, the call should automatically go on hold.
• Transfer Call: transfers the call to a human agent or executive. Use it as transfer_call in the system prompt. A Cold Transfer hands the call over without sharing any conversation context. A Warm Transfer first gives the human full context — the customer’s issue, actions taken, and what is still needed — and hands over once the human gives a go-ahead.
• End Call: ends or hangs up the call from the agent’s side once its task is done. Write a short description telling the agent when to end the call. Example: “Execute this function to end the call when the data is collected for loan profiling, or when the customer asks you to end the call.”
• Check for Availabilities (cal.com): lets the agent check available time slots for a meeting on cal.com. Required inputs: an API key and an Event Id.
• Book a Meet (cal.com): lets the agent book a calendar slot or schedule a meeting on cal.com. Required inputs: an API key and an Event Id.
• Custom Function: comes in two types. Basic is for hitting an API during the call to perform an action — like fetching inventory, listings, or product details. Advanced overcomes the limits of basic custom functions, giving almost unlimited flexibility to build any in-call function from scratch, including custom code to check inputs and modify or format the API’s output before returning it to the agent.

Some examples of Advanced custom functions:

• Formatting: hit an API that returns ISO date-time slots, then reformat those slots into a human-readable format.
• Calculation: compute variable values in real time from customer-specific data — like working out a personalised loan interest rate from the customer’s CIBIL score and monthly salary captured live on the call.
• Dummy Manager Interaction: a simulated hold where the agent tells the customer it needs to consult a senior. During the hold, custom music can play to build trust, and after some time the calculated result is returned — as if a manager was involved.

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Audit function behavior