What needs to be checked is that the site has actual referrals. Also, it should not promote "alternative" products because in my view, that gives a slant as to their neutrality.
Here are some that I have found to be good and helpful for my own reviews, although nobody is perfect.
This is my favorite, but as I mentioned before, nobody is perfect.
Very good. Just enter the website you want to check and off you go. It seems it is supported by a grant of the US Government' National Science Foundation.
This just for starters and I'll be updating regularly.