Did you choose the MSP430 because it is a ultra-low-power microcontroller?
If not I would recommend programming everything on a ESP32.
And ESP32 has a RTC onboard and can be put into a deep-sleep-mode in which the board just consumes something around 150 µA. Depending on the board-type this could be reduced down to 25 µA.
If you insist on keeping the MSP430,
I would not recommend using the AT-firmware. It will be much easier to write a program with the arduino-IDE that does the data-exchange with your MSP430 over a serial interface. On this path you can control every detail of the serial data-exchange and the behaving of the WiFi-part.
For the ESP32 standanlone-version
There are libraries for sending the data to ThingSpeak
best regards Stefan