Hello,
We made some change to Echo api recently. The api ApiEchoNotifications mixed both read and write actions, we have migrated the 'markasread' action to its own api module - ApiEchoMarkRead. The 'markasread' function still works in ApiEchoNotifications but it will be removed once all external api calls have been migrated to the new API.
Example about how to use the new API is in here: https://git.wikimedia.org/blob/mediawiki%2Fextensions%2FEcho.git/40ea204cdc6...
Thanks,