A GNU tools developer is responsible for creating, maintaining, and improving software tools under the GNU project, which focuses on free software. These developers work on compilers, debuggers, libraries, and other essential utilities. They focus on enhancing software functionality, debugging issues, and ensuring compatibility across different platforms. They also collaborate with other developers to manage code contributions, reviews, and testing processes. Moreover, they often provide user support, address bug reports, and develop documentation. They uphold the principles of open-source development, promoting software freedom and sharing.