Send Message

warning

Inbox management is not available on the Basic plan. Upgrade to Intermediate, Growth or Business plan to access this endpoint.

Overview

The Send Message endpoint sends a text reply to an existing Facebook, Instagram, or WhatsApp conversation. This allows you to respond to messages in your inbox via the API.

Base URL:

https://message.oneupapp.io

Endpoint

POST /api/conversations/{id}/messages

Request Parameters

Parameter	Required	Type	Description
apiKey	Yes	string	Your personal API key generated from the API Access page. Passed as a query parameter.
id	Yes	integer	The conversation ID returned by Fetch Conversations. Passed in the URL path. Use id, not conversation_id.
message	Yes	string	The reply text. Required and cannot be empty. Maximum: 4096 characters; platform limits also apply.

Facebook and Facebook-linked Instagram replies use human-agent messaging. WhatsApp replies require a customer message received within the last 24 hours. To send an approved template, use Create WhatsApp Conversation. Sending a template does not open the 24-hour reply window.

Sample Request

curl --location --request POST \
"https://message.oneupapp.io/api/conversations/123/messages?apiKey=YOUR_API_KEY" \
--header "Content-Type: application/json" \
--data '{
  "message": "Thanks for contacting us!"
}'

Sample Response

{
  "message": "OK",
  "error": false,
  "data": {
    "message": {
      "id": 456,
      "conversation_id": "t_987654321",
      "message_id": "m_123456",
      "sender_id": "104040148726689",
      "receiver_id": "987654321",
      "sender_name": "My Page",
      "receiver_name": "Jane Doe",
      "message": "Thanks for contacting us!",
      "attachments": null,
      "template": null,
      "profile_image": null,
      "is_read": 1,
      "created_time": "2026-09-28 10:00:00"
    },
    "outcome": "accepted"
  },
  "meta": []
}

If the connected Facebook or Instagram account needs to be synced, the API returns 202 Accepted with Retry-After: 5. Wait at least five seconds, then repeat the request. See the account sync response.

A send returning this setup response has not sent or queued a message. Repeat it after setup completes.

Response Fields

Field	Description
message	The saved message object.
outcome	accepted when the platform accepts the message. This does not confirm delivery.

Message Object

Field	Description
id	The internal message ID.
conversation_id	The platform-specific conversation identity.
message_id	The platform-specific message ID.
sender_id	The sender’s platform ID.
receiver_id	The recipient’s platform ID.
sender_name	The sender’s display name, when available.
receiver_name	The recipient’s display name, when available.
message	The message text.
attachments	Attachment details, when available.
template	WhatsApp template details, when available.
profile_image	Profile image, when available.
is_read	Local read status: 0 for unread or 1 for read.
created_time	The message creation time, formatted as YYYY-MM-DD HH:MM:SS.

Error Responses

Status	When
401	Missing or invalid apiKey.
403	Inbox management is unavailable on the Basic plan.
404	The requested resource was not found or does not belong to the authorized user.
422	Invalid parameters or the WhatsApp reply window is closed.
429	The limit of 60 requests per minute per API key was exceeded. Wait for the Retry-After interval.
500	Unexpected error, including failure to save an accepted message.
502	The platform rejected the message or returned no message ID.
503	API key verification or account sync is temporarily unavailable.
504	The send timed out; the platform may have accepted the message.

If a send fails, check data.outcome: rejected, unknown, or accepted. Send failures set retry_safe to false. A timeout may occur after the provider accepts the message. If saving the accepted message fails, the response includes its provider message_id. Check the conversation before resending to avoid duplicates; the API does not provide idempotency keys or automatic send retries.

✅ Result: You have successfully submitted your reply to the platform!