widget_build_url.json

{
    "widget_id": "$arbitrary_string",
    "widget": {
        "creatorUserId": "@user:example.org",
        "id": "$the_same_widget_id",
        "type": "m.custom",
        "waitForIframeLoad": true,
        "name": "My Widget Name Here",
        "avatar_url": "mxc://example.org/abc123",
        "url": "https://example.org/widget.html",
        "data": {
            "title": "Subtitle goes here"
        }
    },
    "layout": {
        "container": "top",
        "index": 0,
        "width": 65,
        "height": 50
    }
}