I looked up the dictionary meaning of a corvette:
1 : a warship ranking in the old sailing navies next below a frigate.
2 : a highly maneuverable armed escort ship that is smaller than a destroyer.
3 : with its modest fuel capacity and marginal seakeeping, a corvette isn’t suitable for long-range operations.
So in reality any warship that fits in to this description (500tons to 3000tons) is a corvette by definition.
Our OPVs will be corvettes. So are our 4 dost class coast guard ships.
It depends (in the strict Naval convention in use these days) much more on endurance (point 3's expected mission parameters) than strict tonnage....to better delineate what is a corvette vs frigate. These vary a bit from navy to navy (given each country's size, territorial water, coastline, EEZ, threat profile etc are all different and impact on definitions of long, mid and short range/endurance in the planning and war gaming)
This is how one of most well-read mentors I know explained it to me some time back.
There leads to quite some overlap between corvette and frigate by tonnage alone.
Consider kamorta corvette (3300 tons) vs type 053 frigate (1700 tons) for example.
But kamorta is a corvette because its bulk derives from payload+weapons based for its planned expected mission profiles (of less range/endurance assigned to frigates in the navy).