Baron created Maatkit, from which Percona Toolkit was forked. Many of the tools and modules were originally written by Baron.
Daniel has been the project’s lead developer since 2008 until 2016.
Frank was a full-time Percona Toolkit developer employed by Percona until 2016.
Carlos has been the project’s lead developer since 2016. He is hired by Percona.
Many people have contributed code over the years. See each tool’s “AUTHORS” section for details.