Can't install tools targeting 3.1

Steps to reproduce

dotnet tool install dotnet-ef --version 3.1.0-preview1.19506.2

Expected behavior

Tool 'dotnet-ef' (version '3.1.0-preview1.19506.2') was successfully installed.

Actual behavior

error NU1202: Package dotnet-ef 3.1.0-preview1.19506.2 is not compatible with netcoreapp3.1 (.NETCoreApp,Version=v3.1) / any. Package dotnet-ef 3.1.0-preview1.19506.2 supports: netcoreapp3.1 (.NETCoreApp,Version=v3.1)
The tool package could not be restored.
Tool 'dotnet-ef' failed to install. This failure may have been caused by:

* You are attempting to install a preview release and did not use the --version option to specify the version.
* A package by this name was found, but it was not a .NET Core tool.
* The required NuGet feed cannot be accessed, perhaps because of an Internet connection problem.
* You mistyped the name of the tool.

For more reasons, including package naming enforcement, visit https://aka.ms/failure-installing-tool

Environment data

dotnet --info output:

.NET Core SDK (reflecting any global.json):
 Version:   3.1.100-preview2-014486
 Commit:    343b2cba36

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.18362
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Users\brice\AppData\Local\Microsoft\dotnet\sdk\3.1.100-preview2-014486\

Host (useful for support):
  Version: 3.1.0-preview2.19517.10
  Commit:  3daa0867ab

.NET Core SDKs installed:
  3.1.100-preview2-014486 [C:\Users\brice\AppData\Local\Microsoft\dotnet\sdk]

.NET Core runtimes installed:
  Microsoft.AspNetCore.App 3.1.0-preview2.19517.21 [C:\Users\brice\AppData\Local\Microsoft\dotnet\shared\Microsoft.AspNetCore.App]
  Microsoft.NETCore.App 3.1.0-preview2.19517.10 [C:\Users\brice\AppData\Local\Microsoft\dotnet\shared\Microsoft.NETCore.App]
  Microsoft.WindowsDesktop.App 3.1.0-preview2.19517.10 [C:\Users\brice\AppData\Local\Microsoft\dotnet\shared\Microsoft.WindowsDesktop.App]

To install additional .NET Core runtimes or SDKs:
  https://aka.ms/dotnet-download

cc @ajcvickers @Pilchie

[zivkan]

We talked about it, but haven’t made the change yet.

However, when I do dotnet new console, dotnet add package newtonsoft.json, edit the csproj to use PackAsTool and then run dotnet pack, I don’t get the warning because the generated nupkg doesn’t have any dependencies.

This suggests that @bricelam’s package does have NuGet dependencies, which itself doesn’t make a lot of sense for a tool as they’re supposed to be self-contained, right?

[wli3]

There is an extra lib folder inside the root of the nupkg