Use
Text transfer parameters are used to pass information in a BAPI (e.g. documentation on a business object type) from the SAP System to a calling program.
Features
To transfer documentation texts you have to create the standardized parameters below:
Base this parameter on the type BAPI_TFRMT. This requires the following fixed values that must all be provided by the BAPI:
Use the reference structure BAPITGB for this parameter.

You can see an example of using text transfer parameters in the BAPI BapiService.FieldhelpGetDocu().