MsgVariantImage
Detected GIF input is delivered as animation on Telegram and converted to silent H.264 MP4 video on WhatsApp. Static WebP is converted to PNG for WhatsApp, Telegram and Twilio MMS. Animated WebP becomes silent MP4 for WhatsApp and Telegram, and GIF for Twilio MMS, so animation is not silently reduced to its first frame. Instagram, Messenger and Web Chatt retain supported GIF/WebP input. WhatsApp WebP stickers use stickerUrl.
Concrete MIME type such as image/jpeg; wildcards such as image/* are not valid.
Optional companion text. Delivered as a caption on WhatsApp, Telegram and Web Chatt; discarded on Instagram and Messenger. Twilio MMS carries text with media subject to carrier support; Brazilian SMS does not support media.
context object
Optional filename; also accepted for Sandbox media.
{
"imageUrl": "string",
"mimeType": "string",
"text": "string",
"context": {
"messageId": "string"
},
"filename": "string"
}