Creates and maintains Architecture Decision Records (ADRs) and high-value technical documentation to capture the context, reasoning, and trade-offs behind significant design choices. It ensures that future engineers and agents understand the 'why' behind codebase decisions, such as technology selections, API changes, or data model designs.
Say it in your own words; the assistant finds this recipe by itself. Examples:
Use this skill when making significant architectural decisions, such as choosing a database, framework, or API style, where the reasoning needs to be preserved for future reference. It is also appropriate when shipping features that change public APIs or user-facing behavior, requiring clear documentation of the intent and constraints. Additionally, use it when onboarding new team members or agents who need to understand the historical context and trade-offs of the codebase.
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 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.
ADRs capture the reasoning behind significant technical decisions. They're the highest-value documentation you can write.
Before creating an ADR, inspect the available repository context for an established convention — existing ADRs, project instructions, and ADR-related configuration or tooling (e.g. an .adr-dir file). An established convention overrides the defaults below. Match:
docs/adr/*.md, Documentation/Decisions/*.rst, a MADR layout, or an adr-tools setup. Match the existing directory, file extension, and markup (Markdown vs reStructuredText).ADR-004-Title.rst, 0004-title.md, …); don't restart at 001 or introduce a second scheme.If the available evidence conflicts, surface the conflict rather than silently introducing another scheme. Only when no convention can be established do you apply the default below.
Store ADRs in docs/decisions/ with sequential numbering (unless the project already uses another location — see above):
# ADR-001: Use PostgreSQL for primary database
## Status
Proposed | Accepted | Superseded by ADR-XXX | Deprecated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)
PROPOSED → ACCEPTED → (SUPERSEDED or DEPRECATED)
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;
}
// 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
/**
* 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 {
// ...
}
For public APIs (REST, GraphQL, library interfaces):
/**
* 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> {
// ...
}
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
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.
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)
Special consideration for AI agent context:
After checking the technical content, review the prose for the people who will use it. Clearer wording must not change the decision or its limits.
| 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. |
After documenting:
LICENSESKILL.mdVendored from addyosmani/agent-skills, commit aeac41d4d005, path skills/documentation-and-adrs, licence MIT. The upstream licence file ships inside the skill.