Feature summary (what you would like to be able to do and where):
Add a parameter "blprop" to API:Backlinks, similarly for example with the parameter "cmprop" of API:Categorymembers.

Use case(s) (list the steps that you performed to discover that problem, and describe the actual underlying problem which you want to solve. Do not describe only a solution):
On French wiki we have some scripts (example) that count the number of backlinks/transclusions/etc for a given page. We are only interested by the count of backlinks. Though, we have to retrieve all the backlinks in order to count them. Currently the API requests retrieve these properties for each page: pageid, ns, and title.

Benefits (why should this be implemented?):
This parameter would let reduce the API payload. We could go as far as using this parameter empty ("blprop=" in URL), which would return an empty object for each backlink, still being countable.