You can use the users/show method with user authentication. Unless you are trying to check a private account, any user token will work with any public user profile. For example, using twurl I can check your account.
$ twurl "/1.1/users/show.json?screen_name=youpioou" | jq '. | {followers: .followers_count}'
{
"followers": 65
}
If an account is protected, then the user token you are using must be able to “see” the account in question.