OK, so #tootdon communicates with this server: https://api.tootdon.ooo
This server is hosted in the USA(!!!)
There are several endpoints: /api/v1/instances gives a paginated list of instances, and seems to be the *only* one that doesn't require authentication.
There's also /api/v1/statuses and /api/v1/users. Not sure how authentication to this API works yet...
By the way, it also appears to be tied with this company: http://mobirocket.com/