This is a powershell thing. If you look in psake.ps1, you should see something along the lines of:
param(
[Parameter(Position=0,Mandatory=0)]
[string]$buildFile = 'default.ps1',
[Parameter(Position=1,Mandatory=0)]
[string[]]$taskList = @(),
[Parameter(Position=2,Mandatory=0)]
[string]$framework,
[Parameter(Position=3,Mandatory=0)]
[switch]$docs = $false,
[Parameter(Position=4,Mandatory=0)]
[System.Collections.Hashtable]$parameters = @{},
[Parameter(Position=5, Mandatory=0)]
[System.Collections.Hashtable]$properties = @{},
[Parameter(Position=6, Mandatory=0)]
[alias("init")]
[scriptblock]$initialization = {},
[Parameter(Position=7, Mandatory=0)]
[switch]$nologo = $false,
[Parameter(Position=8, Mandatory=0)]
[switch]$help = $false,
[Parameter(Position=9, Mandatory=0)]
[string]$scriptPath = $(Split-Path -parent $MyInvocation.MyCommand.path)
)
this is how powershell defines function parameters. If you want to specify a parameter, just specify it by name: