REST API not working for other third parties?

Hello,

A developer of our manufacturer wants to set the tracking codes of their system into our woocommerce with your plugin.
But this is the respons he gave me when looking into the plugin:

We’ve checked the documentation here, and it seems their API support only works for specific tracking providers such as TrackingMore and AfterShip. We don’t use one of these, so this doesn’t seem to be sufficient for us to send up the tracking information

How to use the REST API??