Kathy Jo is right. No site can be 100% accurate, or even 80-90% accurate on a housing price, if they havenâ€™t seen your home, and don't know materials, build quality, view, etc.
No real estate website can tell you what your home is worth, especially in this market when things are going so fast (in most areas). You should always talk to at least two Realtors when listing your home and maybe a third if the prices are more than 10-15% off from each other.
And the listing price is only one reason of many to list with a professional Broker, as they can help you navigate through the offer process, inspection process and add value in many ways in this always changing housing market.
Trust your instincts, which it seems like you have by questioning a value.