Stop Outreach sequences when a prospect books on Calendly

When someone books a meeting through Calendly, I want their active Outreach sequences to stop immediately, so we never keep cold emailing a prospect who already agreed to talk. Trigger this on a Calendly webhook for the invitee.created event, set up with Calendly's Create Webhook Subscription operation so new bookings arrive in real time. From the webhook payload take the invitee's email address, their name, the event type they booked, and the meeting start time. If the payload does not carry everything I need, fill the gaps with Get Scheduled Event, or Get Event Invitee and List Event Invitees for the invitee record.

Find the matching prospect in Outreach using List Prospects filtered on that email address, and include the prospect's owner on the same call so I have the owner's name and email without a second lookup. Email matching is the whole game here. Match on the exact invitee address, and if Outreach returns more than one prospect for it, which happens with duplicate records, handle every one of them rather than picking the first.

For each matched prospect, use List Sequence States to pull every enrollment that prospect has. Only act on the ones that are currently active. For each active enrollment, call Pause, Resume, or Finish Sequence State and finish it. Leave enrollments that are already paused or finished exactly as they are, never resume anything, and never add anyone to a sequence. Keep track of the sequence name behind each enrollment so I can name it in the notification, using List Sequences if I need to resolve a name from an id.

Then post a short Slack message to the prospect owner with the Slack Bot. Look up the owner's Slack account from their Outreach email using Look Up User by Email, then direct message them with Send a Message. Keep it to a few lines: who booked, when the meeting is with the date, time, and timezone exactly as Calendly reports it, the event type they booked, and a plain list of the sequences that were stopped. If I cannot resolve the owner's Slack account, post the same message to a fallback sales channel instead of dropping it.

If no prospect in Outreach matches the invitee email, do not fail quietly. Post to Slack that someone booked a meeting and we could not find them in Outreach, with their name, email, and meeting time, since it usually means they booked from a different address than the one we are sequencing and someone should link it up by hand. Do the same when a prospect matches but has no active enrollments: one line saying nothing needed stopping is more useful than silence.

If finishing one enrollment fails, keep going with the rest and report the failures in the Slack message rather than aborting the run. This should also catch prospects who were only secondary recipients on multi-recipient emails, which the built-in Outreach setting skips.