I've recently started exploring Google Script and Google Ads Script. This is a part of one of the codes available as a resource on Google's website.

'report_fields': [
    {'columnName': 'metrics.cost_micros', 'displayName': 'Cost'},
    {'columnName': 'metrics.average_cpc', 'displayName': 'Avg. CPC'},
    {'columnName': 'metrics.ctr', 'displayName': 'CTR'},
    {'columnName': 'metrics.search_impression_share', 'displayName': 'Search Impr. share'},
    {'columnName': 'metrics.impressions', 'displayName': 'Impressions'},
    {'columnName': 'metrics.clicks', 'displayName': 'Clicks'},

I just added another Reporting Field, metrics.all_conversions:

'report_fields': [
    {'columnName': 'metrics.cost_micros', 'displayName': 'Cost'},
    {'columnName': 'metrics.average_cpc', 'displayName': 'Avg. CPC'},
    {'columnName': 'metrics.ctr', 'displayName': 'CTR'},
    {'columnName': 'metrics.search_impression_share', 'displayName': 'Search Impr. share'},
    {'columnName': 'metrics.impressions', 'displayName': 'Impressions'},
    {'columnName': 'metrics.clicks', 'displayName': 'Clicks'},
    
    {'columnName': 'metrics.all_conversions', 'displayName': 'Conversions'}
  ]

This is the error in the logger: Error: Unknown field metrics.all_conversions