Trying to skip the Messenger widget and hit the Guest API directly. Got a valid access token via OAuth. POSTing to /api/v2/conversations/messaging/contacts/{contactId}/messages returns 401 Unauthorized. The token works fine for GET requests on the same contact. Checked the expiration, still good. JSON payload matches the docs. Is there a specific scope I’m missing for writing messages without the widget?
The issue is almost certainly the scope. The Guest API endpoints are picky. You can’t just use conversation:write or webmessaging:write. You need the specific guest scope attached to that token.
Here’s what the token request needs to look like to get the right permissions:
{
"grant_type": "client_credentials",
"scope": "webmessaging:guest"
}
If you’re using the SDK, make sure you’re initializing the client with that exact scope string. Without webmessaging:guest, the platform rejects the POST even if the token itself is valid for reading.
Also double-check the contactId. If that ID came from a different environment or was generated via the widget, it might not match the ID expected by the direct API call in your current context. But 9 times out of 10, it’s just the missing scope.