Connect Cal.com to Retell AI with an API key: create a never-expiring key, pick the cal.com or cal.eu domain, and verify the workspace connection.
Connecting Cal.com takes one API key and gives you agent functions: your agents check real availability, book appointments, and look up, reschedule, or cancel existing bookings. One workspace-level connection covers every agent, with no key pasted into individual tools. This page covers the API key and the connection itself.
This integration replaces Retell’s built-in Cal.com availability and booking tools, which are being deprecated (as of August 2026). Agents still using them keep working; see the FAQ for how to migrate.
Connect Cal.com when your scheduling runs on it and you want callers handled end to end. It’s the right choice when you want to:
Read live openings to the caller. The agent checks the event type’s slots and offers actual times.
Book while the caller is on the line. After the caller confirms a time, the agent books it and Cal.com sends its usual confirmations.
Reschedule and cancel existing bookings. The agent finds the caller’s booking by email and moves it to a newly confirmed slot, or cancels it.
For example, a dental clinic’s inbound agent looks up tomorrow’s cleaning by the caller’s email, offers the week’s open slots, and moves the appointment to Friday 10am, all in one call.
A Cal.com account that owns the event types you want to book.
Know whether your account is on cal.com or cal.eu (the EU-hosted instance). Create the key on that instance and pick the matching domain when you connect.
Cal.com has announced that cal.eu shuts down on November 1, 2026; enterprise customers keep access through their contracted term. Migrating to cal.com is opt-in. If you migrate, reconnect with a cal.com key and the Cal.com domain.
In Cal.com, go to Settings > Developer > API keys and click + New. Keep the API key tab selected, name the key something descriptive, for example Retell AI, and turn on Never expires; an expiring key silently kills the connection on its expiry date. Create it and copy it right away; Cal.com shows the key only once.
Cal.com's Create an API key dialog, with Never expires turned on.
In the Retell Dashboard, open Integrations, select the Available tab, find Cal.com, and click Connect (Add Account if a connection already exists).
2
Enter the key and domain
Fill in the fields:
Field
Value
Connection name
Alias for this connection; prefilled with Cal.com - API key.
API Key
The key from Step 1.
Domain
Cal.com, or Cal.eu for EU-hosted accounts.
The Cal.com connection dialog: API key plus the domain your account lives on.
Click Connect (Add Account if a connection already exists). Retell tests the key against the Cal.com API.
3
Verify it worked
On success the connection appears on the Connected tab. Your agents can now book against the account — see Cal.com agent functions for the tools and the event type ID the booking tools need.
Confirm the key is current and the Domain matches the instance your account lives on (cal.com or cal.eu). If the key had an expiry date, it may simply have lapsed.
The connection errored after working for a while
Retell flags a connection as errored when Cal.com rejects the key — usually expired or deleted. Open the connection’s settings, paste a fresh key set to never expire, and click Reconnect.
