The Oracle probe documentation does not mention anything about monitoring a PDB and the metrics only show pdb_count.
Is it possible to monitor PDB databases?
Yes PDB databases can be monitored. It is necessary for the database administrator to setup a separate connection for each PDB and use that when creating the profile in the oracle probe configure GUI. Each database to be monitored will need its own profile and connection.
All the oracle probe checkpoints listed in the documentation except pdb_count will work for a PDB database. pdb_count is specific for CDB databases.
The multi-tenant option introduced in Oracle Database 12c allows a single container database (CDB) to host multiple separate pluggable databases (PDB)
This is a copy of my knowledge document
How to monitor an Oracle PDB database.