---

name: powershell-expert description: Develop PowerShell scripts, tools, modules, and GUIs following Microsoft best practices. Use when writing PowerShell code, creating Windows Forms/WPF interfaces, working with PowerShell Gallery modules, or needing cmdlet/module recommendations. Covers script development, parameter design, pipeline handling, error management, and GUI creation patterns. Verifies module availability and cmdlet syntax against live documentation when accuracy is critical.

PowerShell Expert

Develop production-quality PowerShell scripts, tools, and GUIs using Microsoft best practices and the PowerShell ecosystem.

Quick Reference

Script Structure

Copy#Requires -Version 5.1

<#
.SYNOPSIS
    Brief description.
.DESCRIPTION
    Detailed description.
.PARAMETER Name
    Parameter description.
.EXAMPLE
    Example-Usage -Name 'Value'
#>

[CmdletBinding()]
param(
    [Parameter(Mandatory, ValueFromPipeline)]
    [ValidateNotNullOrEmpty()]
    [string[]]$Name,

    [switch]$Force
)

begin {
    # One-time setup
}

process {
    foreach ($item in $Name) {
        # Per-item processing
    }
}

end {
    # Cleanup
}

Function Template

Copyfunction Verb-Noun {
    [CmdletBinding(SupportsShouldProcess)]
    param(
        [Parameter(Mandatory, Position = 0)]
        [string]$Name,

        [Parameter(ValueFromPipelineByPropertyName)]
        [Alias('CN')]
        [string]$ComputerName = $env:COMPUTERNAME,

        [switch]$PassThru
    )

    process {
        if ($PSCmdlet.ShouldProcess($Name, 'Action')) {
            # Implementation
            if ($PassThru) { Write-Output $result }
        }
    }
}

Workflow

1. Script Development

Follow naming and parameter conventions:

• Verb-Noun format with approved verbs (Get-Verb)
• Strong typing with validation attributes
• Pipeline support via ValueFromPipeline
• -WhatIf/-Confirm for destructive operations

See best-practices.md for complete guidelines.

2. GUI Development

Windows Forms for simple dialogs, WPF/XAML for complex interfaces:

CopyAdd-Type -AssemblyName System.Windows.Forms
Add-Type -AssemblyName System.Drawing

$form = New-Object System.Windows.Forms.Form -Property @{
    Text          = 'Title'
    Size          = New-Object System.Drawing.Size(400, 300)
    StartPosition = 'CenterScreen'
}

See gui-development.md for controls, events, and templates.

3. PowerShell Gallery Integration

Search and install modules using PSResourceGet:

Copy# Search gallery
Find-PSResource -Name 'ModuleName' -Repository PSGallery

# Install module
Install-PSResource -Name 'ModuleName' -Scope CurrentUser -TrustRepository

Use scripts/Search-Gallery.ps1 for enhanced search.

See powershellget.md for full cmdlet reference.

Key Patterns

Error Handling

Copytry {
    $result = Get-Content -Path $Path -ErrorAction Stop
}
catch [System.IO.FileNotFoundException] {
    Write-Error "File not found: $Path"
    return
}
catch {
    throw
}

Splatting for Readability

Copy$params = @{
    Path        = $sourcePath
    Destination = $destPath
    Recurse     = $true
    Force       = $true
}
Copy-Item @params

Pipeline Best Practices

Copy# Stream output immediately
foreach ($item in $collection) {
    Process-Item $item | Write-Output
}

# Accept pipeline input
param(
    [Parameter(ValueFromPipeline)]
    [string[]]$InputObject
)
process {
    foreach ($obj in $InputObject) {
        # Process each
    }
}

Module Recommendations

When recommending modules, search the PowerShell Gallery:

Live Verification

You MUST verify information against live sources when accuracy is critical. Do not rely solely on training data for module availability or cmdlet syntax.

Tools to use:

• WebFetch: Retrieve and parse specific documentation URLs (PowerShell Gallery pages, Microsoft Docs)
• WebSearch: Find correct URLs when the exact path is unknown or to verify module existence

When Verification is Required

Step 1: Verify Module on PowerShell Gallery

When recommending or checking a module, use the WebFetch tool to verify it exists:

WebFetch call:

• URL: https://www.powershellgallery.com/packages/{ModuleName}
• Prompt: Extract: module name, latest version, last updated date, total downloads, and whether it shows any deprecation warning or 'unlisted' status

If WebFetch returns 404 or error: The module likely doesn't exist. Use the WebSearch tool to confirm:

• Query: {ModuleName} PowerShell module site:powershellgallery.com

Step 2: Verify Cmdlet Syntax (When Needed)

Microsoft Docs URLs vary by module. Use the WebSearch tool to find the correct documentation page:

WebSearch call:

• Query: {Cmdlet-Name} cmdlet site:learn.microsoft.com/en-us/powershell

Then use WebFetch on the returned URL with prompt:

• Prompt: Extract the complete cmdlet syntax, required vs optional parameters, and PowerShell version requirements

Step 3: Fallback Strategies

If the WebFetch or WebSearch tools are unavailable or return errors:

1. For module verification: Execute Search-Gallery.ps1 from this skill:

   Copy~/.claude/skills/powershell-expert/scripts/Search-Gallery.ps1 -Name 'ModuleName'
   

2. For cmdlet syntax: Suggest the user run locally:

   CopyGet-Help Cmdlet-Name -Full
   Get-Command Cmdlet-Name -Syntax
   

3. Clearly state uncertainty: If verification fails, tell the user:

   "I wasn't able to verify this against live documentation. Please confirm the module exists by running: Find-PSResource -Name 'ModuleName'"

Verification Examples

Good (verified with live data):

"The ImportExcel module (v7.8.10, updated Oct 2024, 17M+ downloads) provides Export-Excel for creating spreadsheets without Excel installed."

Bad (unverified claim):

"Use the Excel-Tools module to export data." ← May not exist!

Documentation Resources

• PowerShell Docs: https://learn.microsoft.com/en-us/powershell/
• Module Browser: https://learn.microsoft.com/en-us/powershell/module/
• PowerShell Gallery: https://www.powershellgallery.com
• GitHub Docs: https://github.com/MicrosoftDocs/PowerShell-Docs

References

• best-practices.md - Naming, parameters, pipeline, error handling, code style
• gui-development.md - Windows Forms, WPF, controls, events, templates
• powershellget.md - Find, install, update, publish modules