I think before you go for any tools to check on measurable performance that you drive from your agile initiatives, the assessment process already begins at the implementation level within the team. Clear and transparent communication within the team that aims at productive iterations is the first thing that helps assess the outcomes of the agile in the operations.
Besides, you can rely on some project management tool that could help you keep track of your measured goals to ensure that your agile strategy is working fine. Besides, you can also check for the customer response, scaling of business, and other factors that can help you understand the performance variations.
Read in detail about the Checklist To Set Up QA Processes In An Agile Environment