First, assess their experience and portfolio – check if they have provided some case studies which are quite similar to your project. Another important factor is the amount of experience a particular vendor has in a specific platform that you want to use, such as Shopify, Magento, and others. Another important factor is the aspect of customer relations and relation handling. It is important that a good agency should be in a position to constantly update the client on the development process and be customer-sensitive. Ensure that they also provide services after the launch, in case of any issues. If one is seeking for an authentic solution to this problem, they could consider the services of an ecommerce development agency such as UKAD. They hold great experience in providing effective e-commerce solutions which make them a great option.