There are several cases for making an HTTP request from a host application to another Atlassian application, for example:

  • Create a Confluence space when a Jira project is created

  • Automatically create Confluence pages for certain types of issues

  • Create release notes when a Jira version is released

  • Automatically decline a pull request when the associated Jira issue is closed as Won’t Fix

Typically these are done through calls to the REST API of the other application, or to a script endpoint. However you can also use remote events, or remote control to do the same thing.

Which approach you use depends on the specifics of the task in hand.