  Recently, there has been increasing interest in using Large Language Models
(LLMs) to construct complex multi-agent systems to perform tasks such as
compiling literature reviews, drafting consumer reports, and planning
vacations. Many tools and libraries exist for helping create such systems,
however none support recursive multi-agent systems -- where the models
themselves flexibly decide when to delegate tasks and how to organize their
delegation structure. In this work, we introduce ReDel: a toolkit for recursive
multi-agent systems that supports custom tool-use, delegation schemes,
event-based logging, and interactive replay in an easy-to-use web interface. We
show that, using ReDel, we are able to achieve significant performance gains on
agentic benchmarks and easily identify potential areas of improvements through
the visualization and debugging tools. Our code, documentation, and PyPI
package are open-source and free to use under the MIT license.
