there are two competing JSON parsers in JMP. You probably want to use the newer JSON Wizard.
Download a representative xxx.json from the API. From JMP's file->open dialog, pick the JSON file type and pick the wizard.
From the wizard, try the guesses. If you can get the dev team to write a pandas-like format, that might make it even easier.
If none of the guesses work, the wizard can import using information you supply about the structure of the JSON, but that requires a bit more study.
The script saved in the table can be used for other similar files, without opening the wizard again.
The file size you describe is not too big; there should be a progress dialog and I'd guess about a minute.
Craige