n8n Approval Gateway: Route Slack, Teams, WhatsApp & Email

Route approvals to Slack, Microsoft Teams, WhatsApp & Email—automatically

The n8n Approval Gateway is a webhook-based approval workflow that sends approve/reject requests to Slack, Microsoft Teams, WhatsApp, and an email-friendly payload. It collects responses via secure resume links, applies a configurable decision policy (with timeout/escalation), and returns the final verdict plus a full audit trail to your calling system.

What this workflow does

• Receives approval requests via a POST to the /approval-gateway webhook (subject, description, approvers, channels, policy, and timeouts).
• Validates input, creates an approval session, and generates an HMAC-signed token to protect approve/reject actions.
• Builds channel-specific messages:
  • Slack using Block Kit-style structured content
  • Microsoft Teams using Adaptive Card formatting
  • WhatsApp Cloud API interactive buttons
  • Email HTML payload with approve/reject links
• Sends requests to Slack and Microsoft Teams via incoming webhooks, and to WhatsApp via the WhatsApp Cloud API.
• Waits for decisions through workflow resume links, or triggers the timeout/escalation path when needed.
• Verifies the signed token, aggregates approver decisions using the selected policy (any/all/majority/first), and returns:
  • Final status (approved/rejected/escalated as dictated by policy)
  • Audit object detailing decisions and outcomes

Use cases

• Approve IT changes or access requests from a SaaS back office across multiple teams.
• Route customer or internal approvals to the right channel (Slack, Teams, WhatsApp) with a single gateway endpoint.
• Enforce decision rules (majority, first approver, any/all) and handle delays with escalation.

Technical details

• Inputs/outputs: Webhook POST to /approval-gateway and webhook response containing the final verdict + audit trail
• Security: HMAC-signed approval tokens (update the signing secret with a long, random value)
• Integrations: Slack Incoming Webhooks, Microsoft Teams Incoming Webhooks, WhatsApp Cloud API, email HTML approve/reject links
• n8n nodes used: Code, Wait, Webhook, Sticky Note, HTTP Request, Respond to Webhook