Daily Retell AI reminder calls for tomorrow's appointments

Build me an agent workflow that places friendly Retell AI reminder calls for tomorrow's customer appointments each morning and reports the outcome to my team in Slack.

Trigger: cron, every weekday at 8am in my local time zone.

Step 1. Use Google Calendar List Events to pull events from my target calendar in the next 24 to 36 hours. I want a slightly wider than 24-hour window so early-morning appointments on the far side of the boundary are not missed.

Step 2. Have the agent filter that list down to genuine customer-facing appointments. Skip internal meetings, all-hands, focus blocks, all-day events, and anything without a phone number in the attendee list, location, or description. This is a judgment call, not a hard rule set, so let the agent reason over the event title, description, and attendees to decide.

Step 3. For each qualifying event, extract the attendee's name, phone number, and appointment time. Normalize the phone number to E.164. If two events share a phone number, treat them as one customer with back-to-back appointments and only call once.

Step 4. For each qualifying event, use Retell AI Create Outbound Phone Call with my reminder voice agent and my Retell phone number. Pass name, appointment time, and location as dynamic variables so the voice agent can speak them naturally. Keep the outbound calls spaced out enough to respect Retell's workspace concurrency, and record the call_id returned for each event so we can look up the outcome later.

Step 5. After the batch is dispatched, wait a few minutes for the calls to complete. Then use Retell AI List Calls filtered to the time window of this run (or Retell AI Get Call for each recorded call_id) to pull the outcome, transcript, and call analysis for every call placed in this run.

Step 6. Have the agent classify each call into one of three buckets based on the transcript and analysis: (a) reminded successfully, meaning a live person heard the reminder, (b) voicemail or no answer, (c) customer explicitly asked to reschedule.

Step 7. Post a single Slack summary via Slack Bot Send a Message to my operations channel. Include the counts for each bucket (how many reminded, how many hit voicemail, how many reschedules) and then a named list of the customers who asked to reschedule with their original appointment time so a human can follow up. Also include a short list of events that were skipped because they had no phone number or looked internal, so nothing is silently dropped. Keep it one message, not one per call.

Inputs I want to configure when I set this up: the source Google Calendar id, the Retell voice agent id, the Retell from-number, the Slack channel id for the summary, the local time zone for the 8am schedule, and an optional @mention for the ops lead when there are reschedules to handle.

Failure handling: if Retell returns an error placing one call, log it and continue with the rest of the batch. If Google Calendar returns zero qualifying events, still post a short 'no reminder calls needed today' Slack message so the team knows the workflow ran.