Dex is a tool developed by the mLab engineers that suggests corrections to your indexes based on logged queries.
Purpose: Diagnostics & Performance Tuning
Maintenance status: Inactive since 2013
Supported MongoDB versions: 2.2 2.4
The most recent known version of Dex is 0.6.1 - it was released 4 years and 8 months ago.
This page is a work in progress. Please bear with me while I bring it up to speed. In the meantime, feel free to leave your thoughts on this tool in the comments below. Or, if you are the developer of this tool, please let me know of any updated information I should have.