BaseX returns XML for URLs like http://localhost:8984/basex/jax-rx/; however, database creation commands or collection creation commands result in text/plain content-type and plain-text being returned in response.
Perhaps it will be useful, in pure XML processing apps, for these responses to also be in XML.
Good hint; I've added this one to our JAX-RX todo list as well (and we might also have a second thought on how collection paths are to be treated within JAX-RX.. after the next release, of course).
Christian