EF Core Tools not working on dotnet core 3 preview 4

.NET Core 3.0 introduces Local Tools:

Local tools are similar to global tools but are associated with a particular location on disk. Local tools aren't available globally and are distributed as NuGet packages.

dotnet Core and, also, EF Core, are evolving fast. It's easy to have several projects/solutions at different dotnet versions. With Local Tools you can configure specific version tools by project.

Steps to configure tool by project:

dotnet new tool-manifest  
#executing this at sln level (or with your projecte) a new .config file is created

#check lasts versions at:
#https://www.nuget.org/packages/dotnet-ef/

dotnet tool install --local dotnet-ef --version 3.1.4
#this will configure dotnet ef tool

dotnet ef
#should run at this point

At this point your ef migrations/database command must runs.

When people clone your repo should run:

dotnet tool restore

Edit:

At this point dotnet core 3 is no longer preview, so select our version accordingly. (Check version)

---

First make sure that,

1. You're using the .NET Core SDK 3.0 Preview, type dotnet --info and see there's a line like,

.NET Core SDKs installed:
  3.0.100-preview4-011223 [C:\Program Files\dotnet\sdk]

2. You ran dotnet restore on the project
3. You are cded to the project's (*.csproj) directory

With Entity Framework Core 3.0 Preview 4, dotnet-ef tool is no longer part of the .NET Core SDK. Uninstall the stable version of dotnet-ef tool (2.2.4 at this point) using,

dotnet tool uninstall --global dotnet-ef

Then install the preview or latest stable, (Check version)

dotnet tool install --global dotnet-ef --version 3.0.0-preview4.19216.3

After that dotnet ef should work fine.