A set of rules for handling APIs, n8n workflows, Google Sheets, stored data, and user accounts in Keymoji.

It is for adding login and account flows, reading or updating Google Sheets, calling webhooks, preparing API data, and showing loading or error states.

It reduces duplicate requests, unsafe account operations, hardcoded service addresses, and unclear error handling.

api-backend — Cursor rule by chooomedia

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/chooomedia/keymoji/api-backend

Clone the repo

git clone --depth 1 https://github.com/chooomedia/keymoji

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.

When invoked 660 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.

Model	Per session	Once invoked
Fable 5	$0.00000	$0.00660
Opus 5	$0.00000	$0.00330
Sonnet 5	$0.00000	$0.00132
Haiku 4.5	$0.00000	$0.00066

Measured yesterday against content hash 489d4c988db7, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

api-backend 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/api-backend.mdc · 66 lines

How it starts

The opening of the file, as written. The whole thing — 66 lines — stays where its author put it; the contents beside it link to each section on GitHub.

API, Backend & Storage Patterns

API Calls — Pflichtregeln

IMMER cachedFetch / cachedFetchAccount aus utils/apiCache.js
KEINE direkten fetch() Calls außer in apiCache.js
KEINE doppelten API-Calls — Daten zwischen Komponenten weitergeben
IMMER try/catch mit user-freundlichen Error Messages
IMMER Loading States

Authentication (OTP / Magic Link)

secureLoginWithMagicLink() — Login initiieren
secureVerifyOTP() / secureVerifyMagicLink() — Code verifizieren
Session Validation vor jeder Account-Operation
Cross-Tab Communication via BroadcastChannel

Account Management

accountStore.js — einziger Ort für Account-Operationen
syncAccountData() nach Login/Update aufrufen
currentAccount Store = Single Source of Truth
Vor jedem API-Call: prepareMetadataForAPI() aus metadataCleaner.ts

n8n / Google Sheets

WEBHOOKS aus config/api.js verwenden — nie URLs hardcoden
Actions: "get" / "read" = read-only (kein Sheets-Write), "update" / "create" = Upsert
Google Sheets Spalten (Top-Level, NICHT in metadata):
- userId, email, tier, createdAt, lastLogin, profile, dailyUsage, metadata, status
metadata JSON enthält: settings, updatedAt, updatedVia, lastSettingsSave
profile JSON enthält: name, avatar
dailyUsage JSON: { date, used, storyUsed, limit, lastReset }

localStorage / Storage

IMMER storageHelpers aus config/storage.js
IMMER STORAGE_KEYS Konstanten — nie String-Literals
DAILY_USAGE_HISTORY = lokale Chart-History (kein API-Feld!)
Quota-Exceeded-Errors immer abfangen

Daily Usage / Chart

dailyUsageStore.js — Zähler für heute, API-Sync
userDataStore.js — persistDailyUsageToHistory() nach jedem Increment
Chart liest aus localStorage.DAILY_USAGE_HISTORY — kein metadata.usageHistory
action: "update" sendet dailyUsage als Top-Level Feld, NICHT in metadata

Performance

cachedFetch mit TTL für alle API-Calls
Debouncing für User Input
Lazy Loading für große Komponenten
$derived für abgeleitete Werte, $effect für Side Effects

Read the full file on GitHub · 66 lines

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.

yesterday First seen · 66 lines · 0 tokens per session scan A 489d4c988db7

Subscribe to this mod's changes

api-backend is a cursor rule published in the GitHub repository chooomedia/keymoji (2 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 660 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.

Backend and APIs

api-backend

Getting it into your agent

What it costs to keep this loaded

Grade A, and why

Nothing flagged

How it starts

API, Backend & Storage Patterns

API Calls — Pflichtregeln

Authentication (OTP / Magic Link)

Account Management

n8n / Google Sheets

localStorage / Storage

Daily Usage / Chart

Performance

What this file has done since we first saw it

Other cursor rules, from other repositories

angular-20

dev-standard

typescript

coolify-ai-docs

python_lib

specs