This is a tutorial shows how to comment on an issue, this can be useful in many cases. For example to mention ceratin persons on creating or escalations.

Steps

1. Create a new Action by clicking CREATE button
2. Enter a name: Comment issue and click CREATE
3. Select Method: POST and URL: <your_base_url>/rest/api/2/issue/{{issue.key}}/comment
   From the Atlassian REST API we can read to comment on an issue we need to call POST /rest/api/2/issue/{{issue.key}}/comment
4. Select Authentication method: Basic Auth, specify a user that has comment permission in the project
5. Add request headers, key: Content-Type with value application/json

6. On the Body section add the following

   {
       "body":"RINT says hi {{issue.assignee.displayname}}!"
   }

7. Click Triggers tab
8. Select ISSUE CREATED event
9. On JQL Condition. When to execute the event(s) write Project = TESTB and to limit the trigger to the TESTB project
10. Click SAVE
11. (Optional) Click Test button, Issue Key needs to be provided and click Send, Then go 3 - View Execution Log.