I think "social informatic tool" would include what we typically refer to as "social media" which would, of course, include Snapchat.
In general, if I'm unclear about an assignment, I'd prefer, if possible, to quickly check in with my teacher before starting work (e.g. I love Snapchat, this is OK, right?).
Whether it's a good choice for your report depends on the scope of the assignment, which is not clear from your question.
My guess is that Snapchat would be a valid and interesting option. You can write about the number of users, how it's accessed/used, features, security issues, data collection, how it compares with other major players (Instagram, Facebook, etc.). I'm not a big Snapchat user, but I think there are interesting areas of comparison in terms of access/permissions (phone number, email, etc.) where Snapchat is pretty laid-back encouraging casual users, while others are much more formal. Similarly, Snapchat users have a pretty small digital footprint, while other options tend to have a lot of stuff floating around out there.