These are some tools I use to generate boilerplate invoices on harvest (https://www.getharvest.com/).
cp config.sample.json config.json # Fill in your creds.
node index.js 2017-12-13
Skip fighting with launchd and just setup via: http://launched.zerowidth.com/
It also can serve as an example of how you can create an invoice using their painful v1 API.