A reporting parameter is a parameter type that has its value driven by a particular dimension in the family model.
Reporting parameters extract a value from a geometric condition and use it to report the data to a formula or as a schedulable parameter.
Length, radius, angle, and arc length are available as reporting parameters. (Arc length can be only labeled as a reporting parameter).
When you create a shared project parameter, you can specify it as a reporting parameter in the Parameter Properties dialog.
For example, you can create reporting parameters for the four length and four angle dimensions in a curtain panel by pattern as shown here.
Then after you place the curtain panel by pattern in a project, you can select a panel as shown here and then display the reporting parameters in the instance properties.
After creating reporting parameters, you can also create a schedule to report the data.
The schedule shown here reports the four angle and four length dimensions parameters for all of the curtain wall panels.