I guess its usage in Twtxt clients could be something like this:

$ webfinger prologic@twtxt.net | jq -r '.links[] | select(.rel=="Self").href'
2023/01/06 02:32:40 Looking up WebFinger data for acct:prologic@twtxt.net
2023/01/06 02:32:40 GET https://twtxt.net/.well-known/webfinger?resource=acct%3Aprologic%40twtxt.net
https://twtxt.net/user/prologic/twtxt.txt

Where a lookup of user@domain would yield the Twtxt feed for that user+domain pair.