Hi Dave,
When there are records available at a node's output pin the Data Viewer shows the fields at an output pin and the corresponding data type. Currently (at Dataverse 3.1.6) you cannot view the metadata at an output pin when there are zero records. This will be available in the next release.
If you want programmatic access to the metadata, the Get Metadata node allows you to obtain the metadata for the output data set of a preceding node. You can also access the metadata within a Transform node, see the Python API help text in the Python scripting > API and script bindings section of your installation's Help or online here.
Regards,
Adrian