Javro provides you a nice autocomplete to write Avro files. Every field is contextualized to prevent you from struggling with every types.
You can also use the highlight feature: place your pointer in a Avro field, to highlight it on the JSON preview.
Javro embed an Avro validator so that errors appear on the bottom of the screen.
You can see all meaningful errors regarding your Avro file, and proposition to correct them.
On the right part of your screen, you can see a preview of your Avro file, with sample values.
This is a nice way to tweak easily your Avro, to see how it will represent.