Yes existing MySQL tooling works with MariaDB. The wire protocol is still the same so existing MySQL drivers work to connect to MariaDB as well.
The reverse situation is also useful. The MariaDB client drivers can connect to both MariaDB and MySQL instances yet are licensed LGPL (vs GPL for the MySQL client drivers) which is great for closed source commercial products (and general license compatibility).
We use it in the in house deployed version of our product (database client in your browser[1]) and will be switching the cloud hosted version over to it soon as well. No issues with it so far.