It's hard to say for sure. Some so-called informant stories could be mixtures of truth and fiction. It often requires further research or background knowledge to determine their authenticity.
The Informant had its roots in reality. But like many movies based on true stories, it took some liberties in the storytelling to create a compelling cinematic experience.
In fact, the movie takes elements from actual occurrences and presents them in a cinematic format. While some artistic liberties might have been taken, the core story has a basis in truth.
The movie The Informant is based on a true story. It takes elements from real-life situations and weaves them into a compelling narrative. But keep in mind that not every detail might be 100% accurate as it's adapted for the big screen.