The CONTENTS command line parameter allows you to specify metadata only (like rows=no in standard import/export), ALL (default), or DATA_ONLY (rows only, no metadata) as input options.
When browsing the alphabetical list of options in the dbms_datapump package there is no CONTENTS parameter nor is there a CONTENTS option for the dbms_metadata.set_parameter() procedure.
After digging for a bit I found the dbms_datapump.data_filter() procedure to work:
DBMS_DATAPUMP.DATA_FILTER( handle IN NUMBER, name IN VARCHAR2, value IN CLOB, table_name IN VARCHAR2 DEFAULT NULL, schema_name IN VARCHAR2 DEFAULT NULL);
DBMS_DATAPUMP.DATA_FILTER(h1,'INCLUDE_ROWS',0,NULL,NULL);
I've left the table name and schema names null to include all. Setting the value = 0 in conjunction with the INCLUDE_ROWS option disables the unloading of data by datapump (metadata_only!)
The description for the INCLUDE_ROWS option for the data filter:
If nonzero, this filter specifies that user data for the specified table should be included in the job. The default is 1.
My next task will be to write some robust data pump job monitoring scripts...