Currently, shared items via FB, google+, or Whatsapp use indiscriminate text extracts from the lead of an article. We have put a lot of effort into developing a 'card' summary for link preview, related pages and hover cards. We should provide that to social sites so that we are putting our best foot forward to potential users:
FB extracts its own, which often looks awful.
Here is an example from FB:
=Acceptance criteria =
 A feature flag that when enabled adds a og:description meta tag to all pages in main namespace. It's disabled by default
 og:description is only added if a feature flag is enabled
 the description should be sourced from TextExtracts or the mobile content service
 verify the description shows up in WhatsApp, Facebook and Twitter shares.
== Developer notes
$out->addMeta( 'og:description', $summaryTextNoHtml);
= Open questions
Ideally we'd use the new summary endpoint from the MCS for this. However it's unclear if we can use this for every page view and how we would go about doing that. We can use the TextExtracts endpoint, but that would provide sub-par summaries.
Some guidance on the right approach from services and infrastructure here would be useful.
Out of scope for this task. We may need to sync with the performance team+ops and let them know we're doing this in case it impacts TTFB.