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.

Companion Script: scripts/create-adr.sh

Creates a sequentially-numbered ADR from the skill's template:

# Basic: creates ADR-001-title.md in docs/decisions/
bash ./scripts/create-adr.sh "Use PostgreSQL for primary database"

# With status (default: Accepted)
bash ./scripts/create-adr.sh --status "Proposed" "API versioning strategy"

# Custom directory
bash ./scripts/create-adr.sh --dir docs/adrs "Title"

The script auto-numbers, derives the filename from the title, and fills in the date and section headers from the ADR template below.

Architecture Decision Records (ADRs)

ADRs capture the reasoning behind significant technical decisions. They're the highest-value documentation you can write.

When to Write an ADR

• 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

Lightweight ADR Format (Preferred for Most Decisions)

Most decisions don't need a full template. If a decision is hard to reverse, surprising without context, and the result of a real trade-off, record it as a single paragraph:

# ADR-014: Use PostgreSQL for write model, read models in Redis

The write model needs ACID transactions (order state changes must be atomic).
PostgreSQL gives us that with a well-understood operational story. Read models
are projected into Redis for sub-millisecond query performance on the dashboard.
We considered keeping everything in Postgres, but dashboard queries would need
complex aggregates that are hard to optimize. Redis lets us pre-compute the
shapes the dashboard needs. Trade-off: eventual consistency between write and
read models (~500ms lag), which is acceptable per ADR-007.

That's it. The value is in recording that a decision was made and why --- not in filling out sections.

Only expand to the full format when:

• The decision had multiple serious alternatives worth remembering
• The consequences are non-obvious and need explicit documentation
• The decision supersedes a previous ADR

When to Offer an ADR

All three of these must be true:

1. Hard to reverse --- the cost of changing your mind later is meaningful
2. Surprising without context --- a future reader will look at the code and wonder "why did they do it this way?"
3. The result of a real trade-off --- there were genuine alternatives and you picked one for specific reasons

If any is missing, skip the ADR.

ADR Template (Full Format)

For decisions that need the full treatment, store ADRs in docs/decisions/ with sequential numbering:

See assets/adr-template.md (L3) for the complete template with status, date, context, decision, alternatives, and consequences sections. Load with: bash ./scripts/skill-toolset.sh resource documentation-and-adrs assets/adr-template.md

ADR Lifecycle

PROPOSED -> ACCEPTED -> (SUPERSEDED or DEPRECATED)

• Don't delete old ADRs. They capture historical context.
• When a decision changes, write a new ADR that references and supersedes the old one.

Inline Documentation

When to Comment

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

/**
 * 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 {
  // ...
}

API Documentation

For public APIs (REST, GraphQL, library interfaces):

Inline with Types (Preferred for TypeScript)

/**
 * 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> {
  // ...
}

OpenAPI / Swagger for REST APIs

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

README Structure

Every project should have a README that covers:

# 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.

Changelog Maintenance

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)

Documentation 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

Common Rationalizations

Red Flags

• 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

Verification

After documenting:

• 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

Source: B67687/agentic-workflows — distributed by TomeVault.