The event

Every invocation carries the widget's configured parameters as top-level fields, a describe flag when the console asks for documentation, and a widgetContext object.

This is AWS's example, verbatim.

{
  "widgetContext": {
    "dashboardName": "Name-of-current-dashboard",
    "widgetId": "widget-16",
    "accountId": "012345678901",
    "locale": "en",
    "timezone": { "label": "UTC", "offsetISO": "+00:00", "offsetInMinutes": 0 },
    "period": 300,
    "isAutoPeriod": true,
    "timeRange": {
      "mode": "relative",
      "start": 1627236199729,
      "end": 1627322599729,
      "relativeStart": 86400012,
      "zoom": { "start": 1627276030434, "end": 1627282956521 }
    },
    "theme": "light",
    "linkCharts": true,
    "title": "Tweets for Amazon website problem",
    "forms": { "all": {} },
    "params": { "original": "param-to-widget" },
    "width": 588,
    "height": 369
  }
}

Times

Every time is epoch milliseconds.

zoom is present only when the user has zoomed a chart. AWS's own sample takes the effective range as timeRange.zoom || timeRange, and so should you. A tool that queries for the dashboard's range should read it from here rather than offering a date picker of its own.

Where a value arrives

Three places, and they are not interchangeable.

Source	Where it lands
The widget's configured parameters	Top level, and repeated under widgetContext.params
A parameter sent by a cwdb-action	Top level. Not inside params
A form field in the widget	widgetContext.forms.all, keyed by the field's name

That is why AWS's Logs Insights sample reads form.query || event.query: the form value if the user typed one, otherwise the configured parameter.

Forms

Form fields travel in widgetContext.forms.all, keyed by name. A field without a name never arrives.

The AWS Logs Insights widget wraps an input named logGroups and a textarea named query in a form, binds a button to a call action, and reads widgetContext.forms.all.logGroups with the top-level field as its fallback.

Whether a form wrapper is required, or every named field in the widget is collected, is unverified.