For me to know what calls to make and what cost each will incur, I have been testing them out to see what they all do.
As an example, these ones work well.
https://www.googleapis.com/youtube/v3/search?order=date&part=snippet&channelId={THE_CHANNEL_ID}&key={YOUR_API_KEY}
https://www.googleapis.com/youtube/v3/videos?part=snippet,statistics,contentDetails,status,player,topicDetails&id={VIDEO_ID}&key={YOUR_API_KEY}
https://www.googleapis.com/youtube/v3/playlistItems?part=id,snippet,contentDetails,status&maxResults=2&playlistId={PLAYLIST_ID}&key={YOUR_API_KEY}
However, some do not seem to work. Which is strange as they do in Google test page.
Here are the ones that did not work for me.
https://www.googleapis.com/youtube/v3/channels?part=brandingSettings,contentDetails,contentOwnerDetails,id,localizations,snippet,statistics,status,topicDetails&forUsername=Google&key={YOUR_API_KEY}
https://www.googleapis.com/youtube/v3/channelSections?part=id,snippet,contentDetails&channelId={THE_CHANNEL_ID}&key={YOUR_API_KEY}
https://www.googleapis.com/youtube/v3/activities?part=contentDetails,id,snippet&channelId={THE_CHANNEL_ID}&key={YOUR_API_KEY}
https://www.googleapis.com/youtube/v3/playlists?part=contentDetails,id,localizations,player,snippet,status&channelId={THE_CHANNEL_ID}&key={YOUR_API_KEY}
Is there something that I am missing?
Also all the calls are only list calls and not OAuth2.0 calls.
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UPDATE:
It seems that they are now working.
No idea why they were not before, but would be nice to find out why, as might be relevant.