Upcoming appointment reminder via WhatsApp API
The scenario sends the client a personalised WhatsApp template before a scheduled visit.
Use case overview
The scenario sends the client a personalised WhatsApp template before a scheduled visit. The message includes the client name, service name, visit date, and visit time. A static URL button opens booking details.
Template example
Hello, {{1}}! Reminder: your appointment for {{2}} is on {{3}} at {{4}}. We look forward to seeing you.
- {{1}}customer name
- {{2}}service or appointment type
- {{3}}visit date
- {{4}}visit time
- “View booking”button — fixed in the Meta template

When to use it
Reach for this scenario when a scheduled visit is approaching and the client needs a timely nudge before the appointment — not at booking time, but as the date draws near and email or SMS reminders are easy to miss. It fits clinics and salons with appointment schedules, field service teams where a missed slot leaves idle staff, and integrators wiring reminder jobs from scheduling systems to WhatsApp templates.
Workflow
- Trigger
The scheduling system detects an approaching visit and fires a reminder event.
event·triggered - Capture event
The system resolves the client phone number and booking fields.
phone:"+…" - Build & send
A personalised template message is built with four body variables and a static URL button.
POST/sendTemplate - Delivered
The client receives the WhatsApp reminder and can open booking details via the button.
delivered - Status tracked
Delivery result is logged for the scheduling system or CRM.
status:"read"

Technical implementation
Prerequisites
- 1MSG API Key · How to get API Key
- WhatsApp Business account · How to Connect WABA
- WhatsApp Template · How to Approve WABA Template
- Customer opt-in · How to Manage Customers Consent
Code examples
#!/usr/bin/env bash
set -euo pipefail
# === Configuration (replace "___" placeholders) ===
API_BASE_URL="https://api.1msg.io" # production 1MSG API base URL
CHANNEL_ID="___" # channel ID from 1MSG dashboard
API_TOKEN="___" # channel JWT token (Bearer)
TEMPLATE_NAME="___" # approved template name
TEMPLATE_NAMESPACE="___" # template namespace (required — send fails without it)
TEMPLATE_LANGUAGE="___" # template language code, e.g. "en"
# === Test data ===
TEST_PHONE="___" # client phone in international format
TEST_CUSTOMERNAME="___" # {{1}} customer name
TEST_SERVICE="___" # {{2}} service name
TEST_BOOKINGDATE="___" # {{3}} booking date
TEST_BOOKINGTIME="___" # {{4}} booking time
PHONE_NORM="$(printf '%s' "$TEST_PHONE" | tr -cd '0-9')"
for pair in "CHANNEL_ID=$CHANNEL_ID" "API_TOKEN=$API_TOKEN" \
"TEMPLATE_NAME=$TEMPLATE_NAME" "TEMPLATE_NAMESPACE=$TEMPLATE_NAMESPACE" \
"TEMPLATE_LANGUAGE=$TEMPLATE_LANGUAGE" "TEST_PHONE=$TEST_PHONE" \
"TEST_CUSTOMERNAME=$TEST_CUSTOMERNAME" \
"TEST_SERVICE=$TEST_SERVICE" \
"TEST_BOOKINGDATE=$TEST_BOOKINGDATE" \
"TEST_BOOKINGTIME=$TEST_BOOKINGTIME"; do
val="${pair#*=}"
if [ -z "$val" ] || [ "$val" = "___" ]; then
echo "Missing configuration value: ${pair%%=*}" >&2
exit 1
fi
done
if [ -z "$PHONE_NORM" ]; then
echo "Error: phone number has no digits after normalization" >&2
exit 1
fi
URL="${API_BASE_URL%/}/${CHANNEL_ID}/sendTemplate"
# params carries body ONLY. Button text is fixed in the Meta template — no button param.
# {{1}} customer name → ${TEST_CUSTOMERNAME}
# {{2}} service name → ${TEST_SERVICE}
# {{3}} booking date → ${TEST_BOOKINGDATE}
# {{4}} booking time → ${TEST_BOOKINGTIME}
read -r -d '' PAYLOAD <<JSON || true
{
"phone": "${PHONE_NORM}",
"template": "${TEMPLATE_NAME}",
"namespace": "${TEMPLATE_NAMESPACE}",
"language": { "policy": "deterministic", "code": "${TEMPLATE_LANGUAGE}" },
"params": [
{
"type": "body",
"parameters": [
{ "type": "text", "text": "${TEST_CUSTOMERNAME}" },
{ "type": "text", "text": "${TEST_SERVICE}" },
{ "type": "text", "text": "${TEST_BOOKINGDATE}" },
{ "type": "text", "text": "${TEST_BOOKINGTIME}" }
]
}
]
}
JSON
RESPONSE="$(curl -s -w '\n%{http_code}' -X POST "$URL" \
-H "Content-Type: application/json" \
-H "Authorization: Bearer ${API_TOKEN}" \
-d "$PAYLOAD")"
HTTP_CODE="$(printf '%s' "$RESPONSE" | tail -n1)"
BODY="$(printf '%s' "$RESPONSE" | sed '$d')"
case "$BODY" in
*'"sent":true'*) ok=1 ;;
*) ok=0 ;;
esac
if [ "$HTTP_CODE" -ge 200 ] && [ "$HTTP_CODE" -lt 300 ] && [ "$ok" -eq 1 ]; then
echo "Message sent to client."
echo "API response: $BODY"
else
echo "Send failed. HTTP status: $HTTP_CODE" >&2
echo "$BODY" >&2
exit 1
fi
Response and delivery status
HTTP 2xx and JSON "sent": true mean 1MSG accepted the message for sending — not that it already reached the customer's phone. Save the id field (looks like wamid.…) to correlate delivery callbacks.
{
"sent": true,
"message": "Sent to [email protected]",
"description": "Message has been sent to the provider",
"id": "wamid.HBgLMzgwNjM5..."
}sentAccepted for sending — not yet on the customer's phone
idStore it; delivery callbacks and
hookInfoare keyed on this
Common errors
| Status | API response | Cause | Fix |
|---|---|---|---|
| 200 | Message was not sent: template is not defined | namespace, template or language is missing from the request body. | Send all three. Take namespace and the exact template name from GET /templates; language is an object: {"policy": "deterministic", "code": "en"}. |
| 200 | template name (…) does not exist in <language> | The template is approved in a different language than the one requested. | Use the exact language code the template was approved in (for example es_MX is not the same as es). Check it in GET /templates. |
| 200 | Message was not sent: provide chatId, phone, bsuid, or username | No recipient the channel could resolve. | Pass exactly one recipient: phone (country code plus number, digits only), chatId (for example [email protected]) or bsuid. |
