When does the session window close?

If the client has not written or replied within 24 hours, sendMessage will fail until a template reopens the chat.

How do I check delivery?

sent: true only confirms acceptance. Track delivery via webhook hooks[] or polling.

What if the message is not delivered?

Log the failed/undelivered hook, verify the session window, then retry or use a template.

Can I connect this to my CRM or backend?

Yes — trigger the API call from your inbound webhook or workflow engine.

WhatsApp Business API for session reply — availability inquiry

This scenario sends a free-text WhatsApp message with sendMessage inside the 24-hour customer service window after the client asks if an item is available.

Try the demo View code example

Use case overview

This scenario sends a free-text WhatsApp message with sendMessage inside the 24-hour customer service window after the client asks if an item is available.

Template example

Hello, {{1}}! «{{2}}» is currently {{3}}. Reply here if you want to reserve, get a restock alert, or see similar options.

{{1}}
client name
{{2}}
product or service name
{{3}}
availability status or expected date

WhatsApp Business API for session reply — availability inquiry

When to use it

Reach for this when a prospect asks whether a product or service is in stock or bookable inside an open WhatsApp chat and the answer must land before they leave for a competitor. It fits sales teams pulling live inventory from OMS or CRM, developers wiring webhook-driven session replies, and agencies handling availability for client catalogs.

Fewer lost sales from slow replies

When an inbound availability question arrives via webhook, your backend resolves the SKU and sendMessage returns the product name and current status as three body variables inside the open 24-hour session, so the client gets an answer in the same thread instead of waiting on a rep.

Live stock instead of stale copy

Unlike a cold-start template, sendMessage carries inventory or slot status pulled from OMS or CRM at send time, so the availability line reflects what is on hand or when restock is expected.

Same-thread next steps without a button

The message invites the client to reply in chat to reserve, get a restock alert, or see similar options, so checkout or booking can continue without leaving WhatsApp.

Consistent availability wording

Every reply uses the same three-variable structure — client name, product or service, availability status or expected date — so reps do not retype ad hoc answers that contradict each other.

Workflow

Status tracked
An inbound client message with an availability question arrives via webhook.
status: "read"
Resolves the SKU
Your backend resolves the SKU and current stock or slot status.
status: "read"
Build & send
A session text message sends the product name and availability summary.
POST /sendMessage
Delivered
The client continues the dialog to reserve or choose alternatives.
delivered

Technical implementation

Prerequisites

1MSG API Key · How to get API Key
WhatsApp Business account · How to Connect WABA
Open 24-hour session window · How the 24-hour window works
Customer opt-in · How to Manage Customers Consent
Webhook endpoint · How to Set Up Webhooks

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)



# === Test data ===
TEST_PHONE="___"                 # client phone in international format · requires open 24-hour session window
TEST_CUSTOMERNAME="___"         # {{1}} customer name
TEST_PRODUCTORSERVICENAME="___"         # {{2}} product or service name
TEST_STATUS="___"         # {{3}} status label

PHONE_NORM="$(printf '%s' "$TEST_PHONE" | tr -cd '0-9')"

for pair in "CHANNEL_ID=$CHANNEL_ID" "API_TOKEN=$API_TOKEN" "TEST_PHONE=$TEST_PHONE" \
            "TEST_CUSTOMERNAME=$TEST_CUSTOMERNAME" \
            "TEST_PRODUCTORSERVICENAME=$TEST_PRODUCTORSERVICENAME" \
            "TEST_STATUS=$TEST_STATUS"; 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}/sendMessage"

read -r -d '' PAYLOAD <<JSON || true
{
  "phone": "${PHONE_NORM}",
  "body": "Hello, Alexey! «Premium Plan license» is currently in stock — ready to ship today. Reply here if you want to reserve, get a restock alert, or see similar options."
}
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.

200 OKResponse

{
  "sent": true,
  "id": "wamid.HBgLMzgwNjM5...",
  "message": "Message accepted for delivery"
}

sent
Accepted for sending — not yet on the customer's phone
id
Store it; delivery callbacks and hookInfo are keyed on this

Delivery itself arrives later, as a separate callback. Register a webhook (POST …/webhook) and 1MSG POSTs status updates to your HTTPS endpoint in a top-level hooks[] payload.

200 OKDelivery status webhook — payload you receive

{
  "hooks": [
    {
      "id": "gBGGeSaGViBfAgnlzOSHEwK9O6F",
      "type": "message",
      "status": "sent",
      "timestamp": "1654864094",
      "recipient_id": "556123122026"
    }
  ]
}

status
sent, delivered, read — or a failure status when applicable
id
Correlates the callback with the id returned by the send call
timestamp
Unix seconds, as a string

If you would rather not receive callbacks, poll GET {base}/{channel}/hookInfo?messageId=<id> instead. In practice delivery often completes within seconds — but the API contract does not guarantee it, so never block a flow waiting on it.

Common errors

Status	Response	Cause
200	Message was not sent: empty body	No body in the request.
200	Message was not sent: provide chatId, phone, bsuid, or username	No recipient the channel could resolve.
200	wrong file	The media could not be fetched or uploaded — not a reachable URL, not valid base64.
403	access denied	The token is wrong, or belongs to a different channel than the URL.
200	Message was not sent: filename	sendFile called without a filename, so the media has no extension to send.