Clara cannot see attachments, see that there is an attachment on a thread, or access data in a hyperlink (with the exception of RSVP for events). This is for both your security and privacy, as well as for Clara's security.
Best practice is to copy relevant information that Clara needs and paste it as part of the email text, or provide text-based guidance (e.g. Tell Joe to check our recruiting website for that info).
If you are on a grandfathered Executive plan and attach something that Clara needs in order to schedule that you can't copy/paste into an email, then call this out in the email request so that manual interventions can be completed. For example, if you are attending a several-day offsite and would like Clara to add events to your calendar, copy/paste the text of the agenda into an email.