Sprint is not a separate entity and hence cannot record description, GOAL and other related details. There should be a field to capture the details related to the sprint.

[Walter Buggenhout · Accepted solution]

A sprint goal field is available on Cloud, but - indeed - not on server yet. See my answer to your other question around this topic here: Sprint Title is limited character field (~30 characters only), which is not enough if Sprint Goal is also required to be included in the field. So one specific field for capturing the Sprint Goal is required..

[Eva Kasiak]

Hey we have launched JIRA Server add on which gives ability to add sprint goal and hide/show it on the active sprint board too. The add on was enhanced by WYSIWYG editor and allow to upload files too. Check marketplace listing