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Send WhatsApp messages and read their status. The backend resolves the sender, the recipient, and the 24-hour window for you, so payloads carry content only. Full reference and live try-it: Karibu WhatsApp API.
One endpoint (POST /messages), one body shape discriminated by type (text / template / media / interactive). Target it with to (first contact) or conversation_id (reply). Sends are async: you get 202 with { message_id, status: "pending" }, then poll GET /messages/{message_id} or receive a webhook.
Templates always go and reopen the 24h window. text / media / interactive need an open window and return 422 WINDOW_CLOSED otherwise. For first contact, send a template.

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Send to a number (first contact)

Provide to. sender_id is optional, the backend resolves it. 
curl -X POST "https://karibu.briq.tz/v1/whatsapp/messages" \
  -H "X-API-Key: YOUR_API_KEY" -H "Content-Type: application/json" \
  -d '{ "to": "255712345678", "type": "template", "template_name": "welcome", "variables": { "1": "Asha" } }'

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Reply in a conversation

Same endpoint, but provide conversation_id instead of to. Sender and recipient come from the thread, so you send content only (no to, no sender_id). 
curl -X POST "https://karibu.briq.tz/v1/whatsapp/messages" \
  -H "X-API-Key: YOUR_API_KEY" -H "Content-Type: application/json" \
  -d '{ "conversation_id": "CONVERSATION_ID", "type": "text", "body": "Thanks, your order ships today." }'
Template reply (reopens the window): 
curl -X POST "https://karibu.briq.tz/v1/whatsapp/messages" \
  -H "X-API-Key: YOUR_API_KEY" -H "Content-Type: application/json" \
  -d '{ "conversation_id": "CONVERSATION_ID", "type": "template", "template_name": "order_update", "variables": { "1": "A1234" } }'
Provide exactly one of to (first contact) or conversation_id (reply). Sending both, or neither, is 422 VALIDATION_ERROR.

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Check status

message_id is the id returned at send time. Status walks pending -> sent -> delivered -> read, or failed. For outbound messages, a paired inbound reply is included once it arrives. 
curl "https://karibu.briq.tz/v1/whatsapp/messages/MESSAGE_ID" -H "X-API-Key: YOUR_API_KEY"
# -> { "data": { "status": "delivered", "provider_message_id": "wamid....", "reply": null } }

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Poll messages and responses

List newest-first across the workspace, or scope to one thread. Filter to inbound to read responses without webhooks. 
curl "https://karibu.briq.tz/v1/whatsapp/messages?conversation_id=CONVERSATION_ID&direction=inbound&since=2026-06-24T00:00:00Z" \
  -H "X-API-Key: YOUR_API_KEY"

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Read receipt

Mark an inbound message read on WhatsApp (the blue ticks), by its internal message_id (the id from GET /messages). The provider id is resolved for you. 
curl -X POST "https://karibu.briq.tz/v1/whatsapp/messages/MESSAGE_ID/read" -H "X-API-Key: YOUR_API_KEY"