Per provider, this API will be deprecated in January 2019. Developers are encouraged to migrate to the Google Photos Library API
From their site: The Picasa Web Albums data API allows client applications to view and update Picasa Web Albums content in the form of Google data API GData feeds. Your client application can request a list of user albums, photos, comments, or tags, edit or delete content in an existing entry, and query the content in an existing entry.
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08-12-18 11:59:53[Brief] Picasa Web Albums Data API to be Deprecated updated with Related API Google Picasa
05-06-15 15:52:33[Sample Source Code] Google Picasa Code Sample updated with Related API Google Picasa
05-06-15 15:47:29[SDK] Google Picasa Client Libraries by Google updated with Related API Google Picasa
30-05-15 11:38:51[Analysis] Why Google's Photos Announcement Has Subtle Relevance To Developers updated with Related API Google Picasa
21-01-15 17:05:59[Mashup] Magic Mosaic updated with Related API Google Picasa
25-09-14 15:30:32[Mashup] 55Photos updated with Related API Google Picasa