Hi,
I have not tested your particular case, but I have sent MQTT messages successfully containing JSON data, so I presume that it could work for your particular case. Be careful though, I think there is a size limitation (although I could be confusing this with FireBase Notifications - I use both)
Alternatively, you could consider using the jRDC2 server if you are querying a Data Server - like mySQL - fast, effective and safe as you can get - very easy to setup and use as well.
Enjoy !!