documentation-and-adrs

name	documentation-and-adrs
description	Captures why-not-what: numbered ADRs with alternatives and consequences, intent comments, TSDoc/OpenAPI, README quick start, and changelog entries for shipped behavior. Use when locking an expensive-to-reverse choice, changing a public API, or leaving context for future engineers and agents. Never a comment-the-what pass; not a marketing-site copy skill.
version	1.0.1

Documentation and ADRs

Overview

Document decisions, not just code. The most valuable documentation captures the why — the context, constraints, and trade-offs that led to a decision. Code shows what was built; documentation explains why it was built this way and what alternatives were considered. This context is essential for future humans and agents working in the codebase.

When to Use

• Making a significant architectural decision
• Choosing between competing approaches
• Adding or changing a public API
• Shipping a feature that changes user-facing behavior
• Onboarding new team members (or agents) to the project
• When you find yourself explaining the same thing repeatedly

When NOT to use: Don't document obvious code. Don't add comments that restate what the code already says. Don't write docs for throwaway prototypes.

Prerequisites

• A project repository with a docs/ directory (create one if missing)
• For ADRs: a docs/decisions/ subdirectory
• For API docs: type annotations or OpenAPI spec tooling already configured

Procedure

1. Decide Whether to Write an ADR

Write an ADR when any of the following apply:

• Choosing a framework, library, or major dependency
• Designing a data model or database schema
• Selecting an authentication strategy
• Deciding on an API architecture (REST vs. GraphQL vs. tRPC)
• Choosing between build tools, hosting platforms, or infrastructure
• Any decision that would be expensive to reverse

If the decision is trivial or easily reversible, skip the ADR.

2. Create the ADR File

Store ADRs in docs/decisions/ with sequential numbering.

Windows PowerShell — create the directory and next ADR file:

New-Item -ItemType Directory -Force -Path docs\decisions
$next = (Get-ChildItem docs\decisions -Filter "ADR-*.md" | Measure-Object).Count + 1
$num = $next.ToString("D3")
New-Item -ItemType File -Path "docs\decisions\ADR-$num-<short-slug>.md"

3. Fill in the ADR Template

Use this template:

# ADR-001: Use PostgreSQL for primary database

## Status
Accepted | Superseded by ADR-XXX | Deprecated

## Date
2025-01-15

## Context
We need a primary database for the task management application. Key requirements:
- Relational data model (users, tasks, teams with relationships)
- ACID transactions for task state changes
- Support for full-text search on task content
- Managed hosting available (for small team, limited ops capacity)

## Decision
Use PostgreSQL with Prisma ORM.

## Alternatives Considered

### MongoDB
- Pros: Flexible schema, easy to start with
- Cons: Our data is inherently relational; would need to manage relationships manually
- Rejected: Relational data in a document store leads to complex joins or data duplication

### SQLite
- Pros: Zero configuration, embedded, fast for reads
- Cons: Limited concurrent write support, no managed hosting for production
- Rejected: Not suitable for multi-user web application in production

### MySQL
- Pros: Mature, widely supported
- Cons: PostgreSQL has better JSON support, full-text search, and ecosystem tooling
- Rejected: PostgreSQL is the better fit for our feature requirements

## Consequences
- Prisma provides type-safe database access and migration management
- We can use PostgreSQL's full-text search instead of adding Elasticsearch
- Team needs PostgreSQL knowledge (standard skill, low risk)
- Hosting on managed service (Supabase, Neon, or RDS)

4. Manage the ADR Lifecycle

PROPOSED → ACCEPTED → (SUPERSEDED or DEPRECATED)

• HARD RULE: Don't delete old ADRs. They capture historical context.
• When a decision changes, write a new ADR that references and supersedes the old one.
• Update the old ADR's Status line to Superseded by ADR-XXX.

5. Write Inline Documentation

Comment the why, not the what:

// BAD: Restates the code
// Increment counter by 1
counter += 1;

// GOOD: Explains non-obvious intent
// Rate limit uses a sliding window — reset counter at window boundary,
// not on a fixed schedule, to prevent burst attacks at window edges
if (now - windowStart > WINDOW_SIZE_MS) {
  counter = 0;
  windowStart = now;
}

When NOT to comment:

// Don't comment self-explanatory code
function calculateTotal(items: CartItem[]): number {
  return items.reduce((sum, item) => sum + item.price * item.quantity, 0);
}

// Don't leave TODO comments for things you should just do now
// TODO: add error handling  ← Just add it

// Don't leave commented-out code
// const oldImplementation = () => { ... }  ← Delete it, git has history

Document known gotchas inline:

/**
 * IMPORTANT: This function must be called before the first render.
 * If called after hydration, it causes a flash of unstyled content
 * because the theme context isn't available during SSR.
 *
 * See ADR-003 for the full design rationale.
 */
export function initializeTheme(theme: Theme): void {
  // ...
}

6. Document Public APIs

For TypeScript, prefer inline TSDoc:

/**
 * Creates a new task.
 *
 * @param input - Task creation data (title required, description optional)
 * @returns The created task with server-generated ID and timestamps
 * @throws {ValidationError} If title is empty or exceeds 200 characters
 * @throws {AuthenticationError} If the user is not authenticated
 *
 * @example
 * const task = await createTask({ title: 'Buy groceries' });
 * console.log(task.id); // "task_abc123"
 */
export async function createTask(input: CreateTaskInput): Promise<Task> {
  // ...
}

For REST APIs, use OpenAPI / Swagger:

paths:
  /api/tasks:
    post:
      summary: Create a task
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateTaskInput'
      responses:
        '201':
          description: Task created
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Task'
        '422':
          description: Validation error

7. Maintain the README

Every project should have a README covering:

# Project Name

One-paragraph description of what this project does.

## Quick Start
1. Clone the repo
2. Install dependencies: `npm install`
3. Set up environment: `cp .env.example .env`
4. Run the dev server: `npm run dev`

## Commands
| Command | Description |
|---------|-------------|
| `npm run dev` | Start development server |
| `npm test` | Run tests |
| `npm run build` | Production build |
| `npm run lint` | Run linter |

## Architecture
Brief overview of the project structure and key design decisions.
Link to ADRs for details.

## Contributing
How to contribute, coding standards, PR process.

8. Maintain the Changelog

For shipped features:

# Changelog

## [1.2.0] - 2025-01-20
### Added
- Task sharing: users can share tasks with team members (#123)
- Email notifications for task assignments (#124)

### Fixed
- Duplicate tasks appearing when rapidly clicking create button (#125)

### Changed
- Task list now loads 50 items per page (was 20) for better UX (#126)

9. Document for Agents

Special consideration for AI agent context:

• CLAUDE.md / rules files — Document project conventions so agents follow them
• Spec files — Keep specs updated so agents build the right thing
• ADRs — Help agents understand why past decisions were made (prevents re-deciding)
• Inline gotchas — Prevent agents from falling into known traps

Pitfalls

Rationalization	Reality
"The code is self-documenting"	Code shows what. It doesn't show why, what alternatives were rejected, or what constraints apply.
"We'll write docs when the API stabilizes"	APIs stabilize faster when you document them. The doc is the first test of the design.
"Nobody reads docs"	Agents do. Future engineers do. Your 3-months-later self does.
"ADRs are overhead"	A 10-minute ADR prevents a 2-hour debate about the same decision six months later.
"Comments get outdated"	Comments on why are stable. Comments on what get outdated — that's why you only write the former.

Red flags to avoid:

• Architectural decisions with no written rationale
• Public APIs with no documentation or types
• README that doesn't explain how to run the project
• Commented-out code instead of deletion
• TODO comments that have been there for weeks
• No ADRs in a project with significant architectural choices
• Documentation that restates the code instead of explaining intent
• Deleting old ADRs instead of superseding them

Verification

After documenting, verify each item:

• ADRs exist for all significant architectural decisions
• README covers quick start, commands, and architecture overview
• API functions have parameter and return type documentation
• Known gotchas are documented inline where they matter
• No commented-out code remains
• Rules files (CLAUDE.md etc.) are current and accurate

Windows PowerShell — check for ADRs and stale TODOs:

# List all ADRs
Get-ChildItem docs\decisions -Filter "ADR-*.md" | Select-Object Name

# Find TODO comments older than today's git state
Select-String -Path "src\*.ts","src\*.tsx" -Pattern "TODO" -SimpleMatch

Expected output: A list of ADR filenames and any TODO matches that need resolution.