We have been using Square Marketing with some of our customers. We want to champion this product but there are several key features missing from this product, one of those being that there is no API to pull the marketing data associated with these campaigns.
When will Square add an API to pull campaign performance metrics such as opens, clicks, etc? If there is no plan, we will soon switch our customers to another marketing solution.
At this time there isn’t an API that can pull the marketing campaign data. At this time we don’t have public roadmaps for feature or releases like this. We’re constantly working to improve our features based on feedback like this, so I’ll be sure to share your request to the API product team. 
Thanks for the quick response! Please let me know if the team shares any details about if/when this might happen. I have a feeling this won’t be built for a while but I’d love for my mind to be changed.
I would like to second this request. Thanks Bryan.