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What is check calendar slots?

The Check Calendar Slots function lets your Voice AI agent query available appointment slots from Cal.com in real-time. When callers ask about availability, your agent instantly fetches open slots and presents options.
Cal.com configuration modal for check_availability_of_slots with a Description (Prompt) box, a Pre-tool message with an English language tab and an Add button, an API key (Cal.com) field, disabled Select Events and Choose Timezone dropdowns, and a Save configuration button

Cal.com configuration for check_availability_of_slots

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Configuration options

Select Events and Choose Timezone dropdowns appear only after entering a valid Cal.com API key.

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How to set up

1

Open Tools Tab

Navigate to Tools Tab in your agent configuration.
2

Add Calendar Availability

Find Calendar Availability in the tool catalog and click Add.
3

Enter API Key

Paste your Cal.com API key. Event types will load automatically once validated.
4

Select Event Type

Choose which event to check - 15 min meeting, 30 min meeting, or your custom events.
5

Set Timezone

Match your Cal.com event timezone for accurate time communication.
6

Write Description

Add a clear trigger description - e.g., “Check available slots when caller wants to schedule a meeting.”
7

Save configuration

Click Save configuration, then Save agent to persist the tool on the agent.

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Example conversation

Caller: “Hi, I’d like to schedule a meeting with your team.”Agent: “Of course! Let me check our available slots for you.”Agent triggers check_availability_of_slots functionAgent: “I have openings tomorrow at 10 AM, 2 PM, and 4 PM. We also have slots on Friday at 11 AM and 3 PM. Which works best for you?”

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Best practices

Detailed descriptions

Use “Fetch available slots when caller wants to schedule or asks about times” instead of just “Check availability”

Match timezones

Ensure Bolna timezone matches Cal.com event timezone to avoid confusion

Add pre-tool message

Set a friendly message like “Just a moment…” so callers know to wait

Test before deploying

Verify slots are being fetched correctly with test calls
Timezone matters! Mismatched timezones cause the agent to communicate incorrect times to callers.

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Next steps

Book calendar slots

After checking availability, book the appointment

Custom functions

Build your own API integrations

Transfer calls

Route calls to human agents

Tools tab guide

Complete guide to configuring functions