Attaching a link to a VK API post?

Question

PHP

Hello. There is such a problem:
When publishing a link in a post with a timer (deferred) via api, the link is not "formatted" (screenshot 1). Request example: /method/wall.post?owner_id=-$group_id&access_token=$token&message=$text&attachments=$url&publish_date=$unix_date&sig=$sig"
If you make a similar request, but without publish_date, that is, do not debug, but publish directly to the wall - the link is being formatted (screenshot 2)
What could be the problem?