n8n Workflow: Qualify SMS Replies & Book Interviews with Retell + Google Calendar

Automatically qualify SMS replies and book interviews with Retell + Google Calendar

This n8n workflow listens for inbound Twilio SMS replies, Retell call_analyzed events, and Twilio status callbacks—then verifies signatures, qualifies candidates from screening answers, and books interviews directly into Google Calendar. Qualified candidates are recorded back to your ATS and your team is notified via Slack and Gmail.

What this workflow does

• Single webhook endpoint: Receives a POST request on one endpoint for both Twilio (inbound SMS + status callbacks) and Retell (call_analyzed events).
• Security first: Verifies request signatures (Twilio HMAC-SHA1 or Retell HMAC-SHA256). In live mode, invalid or unsigned requests are rejected.
• Normalizes and filters events: Converts incoming payloads into a common event format, detects SMS opt-out/positive/negative intent, ignores non-actionable delivery receipts and non-final call events.
• Opt-out handling: If a candidate opts out, the workflow records the phone number opt-out in Supabase to stop future outreach, and can send a single confirmation message.
• Candidate qualification: Evaluates Retell structured screening answers (and SMS intent where applicable) against your QUALIFY rules to mark candidates as qualified, needs review, or not qualified.
• Interview booking: For qualified candidates, selects the job’s recruiter, proposes the next available slot, books the interview in Google Calendar, and (when writeback is enabled) records the appointment in Supabase.
• ATS and recruiter notifications: Queues and posts outcome notes (and optional status updates) to the ATS, then alerts recruiters via Slack and Gmail.

Use cases

• SMS-based candidate responses to structured screening questions.
• Automated scheduling after Retell call analysis (no manual calendar chasing).
• GDPR/consent-safe opt-out workflows for SMS outreach.
• Recruiter alerts when candidates qualify or require review.

Technical details

• n8n nodes include: webhook, if, code, merge, gmail, and sticky note.
• Integrations: Twilio, Retell, Supabase, Google Calendar, Slack, and Gmail.