Microsoft launched a fun new tool today, but it doesn’t work quite always work as well as you may think. The company launched How-Old.net, which allows users to put in photos and an algorithm gets to work to guess the age of the people in it.

Microsoft is urging people to share the results on Twitter with the hashtag #HowOldRobot and it’s already trending as people have realized that it’s not really that good at guessing the ages of celebrities. It can also vary widely from photo to photo.

A search for Bill Murray finds that the recent pictures of him get pretty close to his real age. He’s 64 and one photo put him at 66.

Sandra Bullock might like to know that the bot sees her as younger. The 50-year-old star, who was just named People’s Most Beautiful, came up as 36 with one photo.

Athletes seem to be a bigger problem for the bot. When you search for Mike Trout, the 23-year-old star on the Los Angeles Angels, he comes up as 64. That’s a pretty big difference.

Microsoft notes that it is still working on the system. It uses Face APIs, part of Microsoft Project Oxford, which produces algorithms to process facial images. It can also be used for facial recognition and grouping faces of one person together.

The tool is also one way to get people to actually use Bing image search.

screenshots from how-old.net