# authz

Guides access control architecture by separating permission decisions from enforcement.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · ★ 24
- Author: rainmanjam
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/rainmanjam/poka-yoke/tree/HEAD/benchmarks/controls/clean-code/skills/authz/SKILL.md
- Updated: 2026-10-14
- HTML: https://affpapa.org/en/nevibecode/skills/rainmanjam-authz

## What it does

The skill establishes conventions for permission logic. Its core rule dictates that any routine evaluating whether an actor can execute an operation must never execute that operation itself. Isolating the check eliminates scattered boolean logic and turns ambiguous conditions into dedicated, explicit rules with closed-by-default outcomes.

It insists on passing the actor explicitly as an argument instead of reaching into ambient context. When background jobs call functions relying on global state, the result is a runtime `null` crash rather than a clean permission rejection. Typed identifiers for resources prevent swapped argument bugs at compile time.

A clear test of this design is whether authorization rules can run against an input-output matrix without a live server. Coupling rules to transport or database sessions breaks testability immediately.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill authz -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/authz/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/authz/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill authz -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/authz/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill authz -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/authz/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install rainmanjam/poka-yoke authz
```

2. **Manually: put the files in place**
- File: `.github/skills/authz/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill authz -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/rainmanjam/poka-yoke --path benchmarks/controls/clean-code/skills/authz
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/authz/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add rainmanjam/poka-yoke --skill authz -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/rainmanjam/poka-yoke/tree/HEAD/benchmarks/controls/clean-code/skills/authz/SKILL.md

## When to use it
- Separate authorization decisions from business action execution
- Eliminate scattered inline boolean checks across handlers
- Build serverless unit tests covering denied access cases
- Prevent ambient context lookups for current actor identities

## Example prompts
- Review permission checks in `src/services/billing.ts` against the authz skill
- Refactor document deletion rules to avoid reading the actor from global session state
- Generate an actor-action-resource decision matrix for the new workspace endpoint

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: a1ff9976927658f8.

BEGIN THIRD-PARTY FILE a1ff9976927658f8
```text
---
name: authz
description: >-
  Permission and access-control code. Structure, clarity and testability of authorisation
  logic: where the decision lives, how it is named, and keeping it separable from the code
  that acts on it.
---

# Authz: Structuring Access Control

Authorisation code is where structural sloppiness costs most, because a permission check that
is hard to read is a permission check nobody re-reads. The discipline here is the ordinary one,
applied somewhere the consequences are unusual.

## Put the decision in one place

**Separate deciding from enforcing.** A function that answers "may this actor do this thing to
this resource" should not also perform the thing. Once separated, the decision can be tested
exhaustively, listed, audited, and reused by a second caller without dragging the action along.

**One vocabulary for actors, actions and resources.** If some code says `user`, some says
`account`, and some says `principal`, a reader cannot tell whether they are the same concept.
Pick the words and use them everywhere, including in the database columns.

**Avoid boolean soup.** `if (user.isAdmin || (user.isOwner && !resource.locked))` scattered
across twelve call sites is twelve places to update and twelve chances to differ. Name the
rule once: `canEditResource(user, resource)`.

**Make the decision total.** A function returning `true`, `false` or `undefined` will be used
as though `undefined` is one of the other two. Return a decision that covers every case, and
make the default deny rather than allow, because a missing branch should fail closed.

## Structure that makes the check hard to skip

**Take the actor as a parameter, never from ambient context.** A function reaching for a global
`currentUser` can be called from a background job that has none, and the failure will be a
`null` reference in an unrelated place rather than an authorisation error.

**Pass the actor down the call chain rather than re-fetching it.** Re-fetching invites two
layers to disagree about who the actor is.

**Keep the resource identity typed.** A function taking two adjacent strings for
`resourceId` and `ownerId` accepts them in either order. Distinct types make the transposition
a compile error rather than a security incident.

## Make it testable, then test the negative cases

The structural test of an authorisation design is whether you can write a table of
`(actor, action, resource) -> expected` cases and run it without a server.

If you cannot, the decision is tangled with transport, persistence or session handling, and the
first thing to fix is that tangle rather than any individual rule.

The cases that matter are the ones that should be denied. A test suite that only covers
permitted actions passes just as happily against a function that returns `true` unconditionally.

## What good output looks like

- **Name the decision function and its signature.** Where the decision lives is most of the design.
```
END THIRD-PARTY FILE a1ff9976927658f8

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