Custom attributes attached to PowerShell function

Custom-Attribute.ps1

Add-Type -TypeDefinition @"
namespace PoshBot {
    public class BotCommand : System.Attribute {
        public string Description { get; set; }        
    }
}
"@

function Foo {    
    [PoshBot.BotCommand(Description = 'This is a custom function description')]
    [cmdletbinding()]
    param(
        [PoshBot.BotCommand(Description = 'This is a custom parameter description')]    
        [parameter(mandatory)]
        [string]$Name
    )

    Write-Output $Name
}

function Get-ParameterMetadata {
    param (
        [parameter(mandatory)]
        [System.Management.Automation.FunctionInfo]$Command,

        [parameter(mandatory)]
        [string]$ParameterName
    )

    $param = $Command.Parameters.$ParameterName
    if ($param) {
        $param.Attributes | Foreach-Object {
            if ($_.TypeId.ToString() -eq 'PoshBot.BotCommand') {
                $_
            }
        }
    }    
}

function Get-CommandMetadata {
    param (
        [parameter(mandatory)]
        [System.Management.Automation.FunctionInfo]$Command
    )

    $attrs = $Command.ScriptBlock.Attributes
    $attrs | ForEach-Object {
        if ($_.TypeId.ToString() -eq 'PoshBot.BotCommand') {
            $_
        }
    }
}

$cmd = (Get-Command -Name Foo)

Get-CommandMetadata -Command $cmd

Get-ParameterMetadata -Command $cmd -ParameterName Name