It works great now. Turns out I was missing an opening curly brace after require. Thanks everyone!
{
"version": "0.1.0",
"name": "JaxSite",
"description": "Custom template for JaxSite integration.",
"authors": [
{
"name": "JaxSite",
"url": "http://www.jaxsite.com"
}
],
"require": {
"blesta": ">=3.2.0"
}
}