AWS IAM — Common Pitfalls Agent Skill

Provides verified corrections for IAM behaviors that AI agents frequently get wrong — policy evaluation edge cases, trust policy gotchas…

Context cost
1.7k tokensestimated from the bundle, loaded when it triggers
Bundle
1 file · 6.9 kBtext throughout, nothing executable
Licence
Apache-2.0the author’s own terms
Last change
—v2
Servers it uses
Noneruns standalone

What it does

Provides verified corrections for IAM behaviors that AI agents frequently get wrong — policy evaluation edge cases, trust policy gotchas, STS session limits, Organizations quirks, and SAML/MFA specifics. Also provides structured workflows for IAM role management and baseline policy generation from application source code or a Terraform plan JSON. Covers condition operator safety (ForAnyValue/ForAllValues with Null checks), bucket policy deny patterns (VPC endpoint restrictions, org paths), confused deputy protection, and service role creation for AWS services (Glue, CloudTrail, Lambda, ECS…

What this skill changes about the agent has not been set out here as a list. Its SKILL.md, shown below, says it in the author’s own words.

awscloud
Filed under

Cloud & DevOps

The skill itself

A skill is instructions the model reads, so you can see what you are getting: below is the start of its SKILL.md. The front matter loads with every session, the body loads when the skill triggers, and the whole file comes with the install.

SKILL.md6.9 kB · preview
--- name: aws-iam metadata: version: "2" ---
21# AWS IAM — Common Pitfalls
22
23## About This Skill
24
25This skill contains verified corrections for things that AI agents frequently get wrong about IAM. It is not a comprehensive IAM guide — for full IAM guidance, search AWS documentation. When answering IAM questions, verify specific claims (limits, quotas, exact API names, edge-case behaviors) against official AWS documentation rather than relying on pre-training. Prefer fetching known documentation URLs over broad searches. Trust official documentation over memory when they conflict.
26
27## Common Workflows
28
29Use the best available tool for AWS operations — the AWS MCP server is recommended but not required; AWS CLI or SDK may be used as alternatives. Read reference files only when the conversation requires deeper detail.
30
31- Read [references/aws-iam-role-management.md](references/aws-iam-role-management.md) if the user needs to create, scope, or maintain IAM roles when provisioning or updating AWS resources. Covers service roles, execution roles, trust policies, confused deputy protection, and permission hygiene.
32
33- Read [references/aws-iam-policy-generation.md](references/aws-iam-policy-generation.md) if the user needs to generate IAM policies, determine required IAM actions for API calls, or understand action-to-operation mappings. **CRITICAL: If the user provides application source code (in any language) or a Terraform plan JSON file (terraform show -json output), you MUST read this reference — it mandates using iam-policy-autopilot instead of manual policy construction.** Uses the programmatic service authorization reference for accurate mappings.
34
35## Verified Edge Cases
36
37**CloudTrail:**
38
39- AcceptHandshake/DeclineHandshake logged in ACTING account ONLY, not management account. Organization trail required for centralization.
This is a preview of SKILL.md. Download or install the skill to get the whole thing.
In the file
SKILL.md839 words
Files1
LicenceApache-2.0
Why you can read it

Nothing in a skill executes. The client loads the text and the model follows it, so a skill can be audited the way a runbook is — by reading it.

What it costs in context

Skills are not billed by the call. They are paid for in context: every token the instructions occupy is a token your code, your diff and your conversation cannot use. Here is what this one takes and when it takes it.

≈270
always loaded
The name and description, so the model knows the skill exists and when to reach for it.
1,455
on trigger
The instruction body, read only when the skill fires.
0.86%
of a 200k window
Ten skills this size would take about 9% of the window before you open a file.
050k100k150k200k context window

1.7k tokens, estimated from the bundle at four bytes to the token, held for the rest of the session once it triggers. Middling. Fine to keep on in a project where you use it weekly, worth unloading in one where you never do.

Servers bill, skills cost

A server charges by the month. A skill charges once per session, in context, and then keeps charging it for as long as the session lives.

Before and after

The same question, put to the same model twice: once as it comes, and once with these instructions loaded.

No worked example has been published for this skill yet.

The procedure it runs

The procedure has not been set out here step by step. It is in the body of its SKILL.md: the start of it is shown above, and the whole file comes with the install.

Prose, not code

These steps are written for a model to follow, not executed by a runtime. It can still be told to skip one, and it will say so when it does.

Servers it uses

None. This skill calls no MCP servers at all.

Everything it needs is in the instructions, so it works in a project with nothing connected — the model reads the file and changes how it works with what it can already reach.

Its SKILL.md does not declare which tools it asks the agent for, so what it touches is whatever the instructions themselves ask for — read them before you install it.

What it asks for
Writes filesnot declared
Network accessnot declared

This SKILL.md carries no allowed-tools line, so neither is declared. A skill grants no permissions of its own — it can only ask for tools your client already has.

What it will not do

Every skill is narrow, and the useful ones say where they stop. These are the jobs this one is the wrong tool for.

What this skill is not for has not been published here. Nothing is implied by that: it is a section the author has not filled in.

What is in the bundle

1 file, 6.9 kB on disk. A bundle is text throughout: the instructions the model reads, plus the templates it fills in.

  • SKILL.md6.9 kB
What is not in it

No dependencies and nothing executable: a skill is text the agent reads, so the bundle is 1 file you can review in full before installing. The Apache-2.0 licence covers the templates and examples as well as the instructions.

Install

Installing copies the bundle into your project. Nothing runs at install time — the files sit on disk until the model reads them.

# AWS IAM — Common Pitfalls · 1.7k tokens when loaded · macOS, Linux mkdir -p .claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/aws-iam-common-pitfalls/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/aws-iam-common-pitfalls" ] && { [ ! -e .claude/skills/aws-iam-common-pitfalls ] || { mv .claude/skills/aws-iam-common-pitfalls "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/aws-iam-common-pitfalls" .claude/skills/ && echo "Installed .claude/skills/aws-iam-common-pitfalls"
On Windows, or any OS with Node 20+
npx mcprush@latest skill add aws/aws-iam-common-pitfalls

Windows PowerShell says 'running scripts is disabled on this system'? Run Set-ExecutionPolicy -Scope CurrentUser RemoteSigned once, or type npx.cmd instead of npx (codex.cmd, gemini.cmd, grok.cmd likewise). PowerShell 7 needs neither. Writes to .claude/skills/aws-iam-common-pitfalls/ in the current project. For every project instead, run mkdir -p ~/.claude/skills && t=$(mktemp -d) && curl -fsSL -o "$t/bundle.tar.gz" https://mcprush.com/api/skills/aws-iam-common-pitfalls/bundle.tar.gz && tar -xzf "$t/bundle.tar.gz" -C "$t" && [ -d "$t/aws-iam-common-pitfalls" ] && { [ ! -e ~/.claude/skills/aws-iam-common-pitfalls ] || { mv ~/.claude/skills/aws-iam-common-pitfalls "$t/.previous" && echo "Previous copy moved to $t/.previous"; }; } && mv "$t/aws-iam-common-pitfalls" ~/.claude/skills/ && echo "Installed ~/.claude/skills/aws-iam-common-pitfalls" (macOS, Linux) — or add --global to the npx line. The curl line replaces .claude/skills/aws-iam-common-pitfalls/ only after the download succeeds, so files left there by another skill of the same name, or by an older release, do not mix in. A copy already there is moved aside, not deleted, and the line prints where. It appears as aws-iam in Gemini CLI, Codex, Copilot and Grok (its own name); Claude Code lists it by the folder name, aws-iam-common-pitfalls.

Which clients pick it up on their own

A skill is a folder of text. Most of these read a skills folder and pick it up without being told; the rest take the same folder another way — an upload in the app, a parameter on an API call — and then choose it by its description just the same.

Claude Code.claude/skills/
Claude DesktopCustomize › Skills
ChatGPTSkills › Create › Upload
Cursor.cursor/skills/
VS Code.github/skills/
Codex CLI.agents/skills/
Gemini CLI.gemini/skills/
Grok Build.grok/skills/
Microsoft CopilotSkills › Upload a skill
PerplexityComputer › Skills › Upload a skill
DeepSeek Harness.dsh/skills/
Zed.agents/skills/
Devin Desktop.devin/skills/
Windsurf (legacy).windsurf/skills/
OpenAI Agents SDKInstructions or sandbox Skills
HTTP / APIa request parameter
This release
Version2
Publishedno release date on file
PriceFree
Referenceaws/aws-iam-common-pitfalls

Versions

v2 is what is on the shelf; no release here carries a date. Instructions change more often than APIs do — a skill can be rewritten entirely without anything it depends on moving.

v2
  • No earlier releases have been published to the marketplace.
Pinning

The install command always fetches the release that is current the day you run it — v2 today — and cannot ask for an earlier one. The copy on your disk does not change until you run it again.

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