This document briefs on how to access the details of issue and transition objects in Jira expressions, such as those available through the issue and transition variables. To see an example of the structure of an issue go to <base_URL_of_Jira>/rest/api/latest/issue/{issueKey}. The fields displayed through this REST API actually depend on the fields set on the issue. Structure of an issue object
An issue object consists of the issue key and a collection of fields. The structure of the issue object (such as those available through the issue and linkedIssue variables) returned in Jira expressions is same as that returned by the /rest/api/latest/issue REST resource documented here. However, only a few data types are supported in the Jira expressions. See here to find all types supported in Jira expressions along with their properties and methods.
Structure of the transition variable
The transition variable describes the current workflow transition. It contains information about the transition that is currently happening and allows to inspect the source and target status. The transition of an issue consists of the following fields:
id: The transition ID (Number).name: The transition name (String).from: The current status of the issue (IssueStatus).to: The target status of the transition (IssueStatus).hasScreen: true if there is a screen configured for this transition, false otherwise (Boolean)