Facebook’s tool that will show you if you liked or followed fake Russian accounts spreading falsehoods during the 2016 presidential election on Facebook or Instagram launched Friday.

The new tool, which is available through its “Help Center,” marks the first time that Facebook users will be able to find out if they were duped by accounts associated with the Russian Internet Research Agency. Nearly 150 million Facebook and Instagram users may have seen paid ads and organic posts distributed by the Kremlin-linked organization in St. Petersburg.

Democratic lawmakers had called on Facebook to inform users whether they were exposed to the Russian disinformation campaign. Facebook announced the tool last month.

How it works: You will be able to see if pages or accounts you liked or followed between January 2015 and August 2017 were created by Russian operatives, who tried to sow discord with posts and ads on race, religion, gun rights, gay rights, immigration and other hot-button issues. Some of the pages and accounts promoted the candidacy of Donald Trump and criticized his Democratic challenger, Hillary Clinton. You’ll either see a message saying you didn’t follow any of the pages or you will get a list of the pages you followed as well as the date you followed them.

The tool has significant limitations. It can’t tell you if you were one of the people who saw this content because friends shared it in your news feed. It only shows you the content the Russian entity targeted at you directly. Also, the tool will not show you the content posted by the accounts or pages, only a list of the content. Facebook has left it up to Congress to release the ads themselves.