When importing via Web API using 'paging[page_size]=50' I receive an error.

When importing via Web API using 'paging[page_size]=50' I receive an error.

Error:  The parameter ZDBSCHURL does not match the accepted input pattern

when I leave off the parameter  'paging[page_size]=50' things work fine, but I'd like to include this parameter when importing on a schedule.  It seems like the issue is because of the brackets but encoding them didn't resolve the error.