patterns

A set of design rules for structuring services, web APIs, and data-access code. It defines response formats, a way to represent expected failures, repositories for database access, and separate application layers.

In plain words
What is it for?
Use it when designing or reviewing APIs and backend services, especially when deciding how handlers, business logic, repositories, errors, and responses should be organized.
Why use it?
It keeps request handling, business rules, and database work separate, making code easier to understand and reducing inconsistent API behavior.

Cursor rule for Cursor

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add rules/jy315189/everything-cursor/patterns
Clone the repo
git clone --depth 1 https://github.com/jy315189/everything-cursor

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 338 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.00338
Opus 5 $0.00000 $0.00169
Sonnet 5 $0.00000 $0.00068
Haiku 4.5 $0.00000 $0.00034

Measured yesterday against content hash c796517b613b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

patterns scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.cursor/rules/patterns.mdc · 51 lines

What it actually says

Design Patterns

API Response Envelope (mandatory for all endpoints)

// Success
{ success: true, data: T, meta?: { page, pageSize, total } }

// Error
{ success: false, error: { code: string, message: string, details?: unknown } }

Result Type (for service-layer expected failures)

type Result<T, E = string> =
  | { success: true; data: T }
  | { success: false; error: E }

// Use Result for: not-found, validation, business rule violations
// Use exceptions for: bugs, infra failures, unexpected errors

Repository Pattern

interface Repository<T> {
  findById(id: string): Promise<T | null>
  findAll(filter?: Partial<T>): Promise<T[]>
  create(data: Omit<T, 'id' | 'createdAt'>): Promise<T>
  update(id: string, data: Partial<T>): Promise<T>
  delete(id: string): Promise<void>
}

Layered Architecture

Handler (HTTP) → Service (Business Logic) → Repository (Data Access)

Handler: parse request, validate input, format response. NO business logic.
Service: orchestrate operations, enforce rules, transaction boundaries. NO HTTP.
Repository: single-entity CRUD, query construction. NO business rules.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 51 lines · 0 tokens per session scan A c796517b613b

Subscribe to this mod's changes

patterns is a cursor rule published in the GitHub repository jy315189/everything-cursor (2 stars, last pushed 6mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 338 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.