You can pass a string of your activity
[RequiredArgument]
public InArgument<string> DirectoryToSearch { get; set; }
In previous versions of TFS, you could simply pass SourcesDirectory or BinariesDirectory
In 2013, the default objects for SourcesDirectory and BinariesDirectory were deleted.
Microsoft.TeamFoundation.Build.Activities.Extensions.WellKnownEnvironmentVariables.
