powershell-windows

A set of PowerShell guidance for Windows scripts, covering operators, empty values, text substitution, and safe script output.

In plain words
What is it for?
Use it when writing or reviewing Windows PowerShell commands and scripts, especially logical checks, null checks, interpolated strings, and ASCII-only output.
Why use it?
It prevents common PowerShell mistakes that can cause incorrect conditions, failures when values are missing, or scripts that do not work as intended.

Skill for Claude CodeCodex

▶ The Rise of Generative UI for Developers (CopilotKit) Better Stack · about vudovn/ag-kit · on YouTube →
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/vudovn/ag-kit/powershell-windows
Any agent
npx skills add vudovn/ag-kit --skill powershell-windows
Clone the repo
git clone --depth 1 https://github.com/vudovn/ag-kit

Made for: Claude Code, Codex.

Per session 19 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,018 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00019 $0.01018
Opus 5 $0.00010 $0.00509
Sonnet 5 $0.00004 $0.00204
Haiku 4.5 $0.00002 $0.00102

Measured 2d ago against content hash a2e47e73f225, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

powershell-windows scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

Copies of this mod

4 near-identical copies found in the catalogue:

.agents/skills/powershell-windows/SKILL.md · 170 lines

How it starts

The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.

PowerShell Windows Patterns

Critical patterns and pitfalls for Windows PowerShell.


1. Operator Syntax Rules

CRITICAL: Parentheses Required

❌ Wrong ✅ Correct
if (Test-Path "a" -or Test-Path "b") if ((Test-Path "a") -or (Test-Path "b"))
if (Get-Item $x -and $y -eq 5) if ((Get-Item $x) -and ($y -eq 5))

Rule: Each cmdlet call MUST be in parentheses when using logical operators.


2. Unicode/Emoji Restriction

CRITICAL: No Unicode in Scripts

Purpose ❌ Don't Use ✅ Use
Success ✅ ✓ [OK] [+]
Error ❌ ✗ 🔴 [!] [X]
Warning ⚠️ 🟡 [*] [WARN]
Info ℹ️ 🔵 [i] [INFO]
Progress [...]

Rule: Use ASCII characters only in PowerShell scripts.


3. Null Check Patterns

Always Check Before Access

❌ Wrong ✅ Correct
$array.Count -gt 0 $array -and $array.Count -gt 0
$text.Length if ($text) { $text.Length }

4. String Interpolation

Complex Expressions

❌ Wrong ✅ Correct
"Value: $($obj.prop.sub)" Store in variable first

Pattern:

$value = $obj.prop.sub
Write-Output "Value: $value"

5. Error Handling

ErrorActionPreference

Value Use
Stop Development (fail fast)
Continue Production scripts
SilentlyContinue When errors expected

Try/Catch Pattern

  • Don't return inside try block
  • Use finally for cleanup
  • Return after try/catch

6. File Paths

Windows Path Rules

Pattern Use
Literal path C:\Users\User\file.txt
Variable path Join-Path $env:USERPROFILE "file.txt"
Relative Join-Path $ScriptDir "data"

Rule: Use Join-Path for cross-platform safety.


7. Array Operations

Correct Patterns

Operation Syntax
Empty array $array = @()
Add item $array += $item
ArrayList add $list.Add($item) | Out-Null

Read the full file on GitHub · 170 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 170 lines · 19 tokens per session scan A a2e47e73f225

Subscribe to this mod's changes

powershell-windows is a skill published in the GitHub repository vudovn/ag-kit (8,162 stars, last pushed 2d ago), licensed MIT. It adds 19 tokens to every session and 1,018 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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