The GRT is a thin C layer, inspired by Objective C, which allows for dynamic typing and dynamic data objects. The GRT is used by the MySQL Migration Toolkit and provides a means for expanding these tools. Through the use of the GRT, these tools can support new behavior and data sources using code written in languages such as C, C++, Java, Python, and Lua with support for Mono forthcoming.

The GRT is not only useful for expanding MySQL GUI Tools. By using a script file from within the GRT shell you can perform repetitive tasks programmatically from the command line. Suppose, for example, that you have multiple schemata that you wish to migrate to MySQL. You can do this once using the graphical interface, in the process saving the procedure as a script file. You can then adapt this script file and run it unattended from the GRT shell.

The preferred development language is Lua, a lightweight scripting language expressly designed for extending applications. For more information about this language see lua.org.