Along with standard RSS 2.0 elements, in order to export data into Yandex a special elemnt "yandex-fulltext" is needed, which should contain full contents of the publication:
Full contents of the publication
To include the full content of publications, the feed must use the additional namespace:
xmlns:yandex="http://news.yandex.ru"
HTML will be placed in the CDATA section.
Full text should not contain the name of the source and date/time of the message, and contact information or any other information, which is repeated in every message.