This endpoint allows you to upload a custom DMOJ APIv2 contest JSON, and it will predict the ratings for that contest. See more information on how ratings are predicted here. You may find this endpoint useful for DMOJ's new partially hidden scoreboard contests.
To get started, go back to the rating predictor custom contest home page here and upload a valid APIv2 contest JSON, which you can find more detail about on DMOJ's API page. You will be redirected to a page with your rating predictions (it may take some time to process your request).
Note: Anyone who has access to your URL will be able to view the rating predictions. Be careful when sharing links to hidden scoreboard contests.