Your startup project doesn't reference Microsoft.EntityFrameworkCore.Design

Question

I have 2 projects in my solution, I have a project with Entity Framework Core installed:

And in the other ASP.NET Web API project I have these packages:

Answer 1

Do you have multiple projects? If yes then you have to make the host project as startup project from solution explorer and set the project as default (which project has DBContext) in PMC. Then run Add-Migration command.