Mismatch Finder is a tool to help editors review potential discrepancies between Wikidata and other databases, websites, etc. It relies on people to write scripts to compare an external data source to Wikidata's data and then upload resulting mismatches to the Mismatch Finder store. Mismatch Finder is intended to help ensure data quality on Wikidata and make the Linked Open Data Web more robust by uncovering potential mistakes in the data.
There are a number of external data sources that people said would be useful to compare to Wikidata's data in order to find potential issues in either data set:
Check Mismatch Finder docs for more explanation about how Mismatch Finder works and how to prepare an upload of mismatches for review.