Source for those json files:
example CMIP6 json file: https://github.com/PCMDI/cmip6-cmor-tables/blob/master/Tables/CMIP6_input_example.json
experiment/activity/parent: https://rawgit.com/WCRP-CMIP/CMIP6_CVs/master/src/CMIP6_experiment_id.html
required global attributes: https://github.com/PCMDI/cmip6-cmor-tables/blob/master/Tables/CMIP6_CV.json
exmplanation to all options: https://goo.gl/v1drZl
source (model) registration: https://rawgit.com/WCRP-CMIP/CMIP6_CVs/master/src/CMIP6_source_id.html