Note: The Checks API only looks for pushes in the repository where the check suite or check run were created. Pushes to a branch in a forked repository are not detected and return an empty pull_requests array.

Lists check runs for a commit ref. The ref can be a SHA, branch name, or a tag name. GitHub Apps must have the checks:read permission on a private repository or pull access to a public repository to get check runs. OAuth Apps and authenticated users must have the repo scope to get check runs in a private repository.
List check runs for a Git reference