Open Graph beta: How can you tag friends in a action?

I've managed to publish an activity using the Graph API. How can you tag friends in a action?

I can see you can add tags in the action dashboard, but other th开发者_高级运维an that it's not specified how to tag friends.

There's a simplified example at https://developers.facebook.com/docs/beta/opengraph/actions/#tagging

Actions can be tagged with places and people by specifying the place and tags optional parameters.

A sample call would be a POST to

https://graph.facebook.com/me/{APP_NAME}:{ACTION NAME}?
  {YOUR OTHER ACTION PARAMETERS HERE}
  &place={A PLACE ID}
  &tags={COMMA SEPARATED LIST OF UIDS}&access_token=YOUR_ACCESS_TOKEN

That would tag the users in the action, and also tag them at a place