express-rules

express-rules is a cursor rule for Cursor from beel-collab/presets.dev. It costs 0 tokens per session (911 once invoked), scanned A, original, MIT.

A set of Cursor instructions for Express projects, covering middleware, routing, validation, errors, security, performance, and tests. Express is a Node.js framework for handling web requests and APIs.

In plain words
What is it for?
Use it when changing Express routes, middleware, request validation, error handlers, and API tests.
Why use it?
It helps keep middleware in the correct order, validate incoming data, and handle asynchronous failures without sending conflicting responses.

Cursor rule for Cursor

Written for Cursor: a Cursor rule (.mdc). Also seen: mentions Codex; mentions Cursor.

Good fit Use it when changing Express routes, middleware, request validation, error handlers, and API tests.

Compare 6 cursor rules from other repositories ↓
Install with agentmods
npx agentmods add rules/beel-collab/presets.dev/express-rules
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.

Clone the repo
git clone --depth 1 https://github.com/beel-collab/presets.dev

Made for: Cursor.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for express-rules

README.md
[![agentmods](https://agentmods.dev/badge/rules/beel-collab/presets.dev/express-rules/github.svg)](https://agentmods.dev/rules/beel-collab/presets.dev/express-rules)
Your own site
<a href="https://agentmods.dev/rules/beel-collab/presets.dev/express-rules"><img src="https://agentmods.dev/badge/rules/beel-collab/presets.dev/express-rules/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for express-rules

Your own site · 80×15
<a href="https://agentmods.dev/rules/beel-collab/presets.dev/express-rules"><img src="https://agentmods.dev/badge/rules/beel-collab/presets.dev/express-rules.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 911 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00000 $0.00911
Opus 5.5 $0.00000 $0.00364
Sonnet 5.5 $0.00000 $0.00182
Haiku 4.5 $0.00000 $0.00091

Measured today against content hash d41eb4a68cb4, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

express-rules 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 today.

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/express/express-rules.mdc · 95 lines

How it starts

The opening of the file, as written. The whole thing — 95 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Express Rules for Cursor: Middleware, Routing and Validation

Install

Install the native export at .cursor/rules/express-rules.mdc. Copy that export, not this catalog file. Catalog fields such as tools and author are for presets.dev. Install one skill file per name. Cursor, GitHub Copilot, Codex, Antigravity CLI, and Devin can all read .agents/skills, so a second copy with the same name collides.

Express Rules for Cursor: Middleware, Routing and Validation

File-scoped Cursor rule for Express. It attaches when a matching file is in context.

Updated for Express 5.3.0, Nov 2026

Do not upgrade dependencies or the framework version unless the task asks.

Project shape

Middleware is an ordered list. Security headers, body parsing, and auth run before the route that needs them. A router mounts on a path. Do not register a catch-all before a more specific route and then wonder why the specific route never runs.

An async handler either uses the project's wrapper or relies on Express 5's rejection forwarding. It does not do both. Do not catch a rejection, send a response, and also call next(err).

Validation and bodies

Validate params, query, and body with the project's schema. Reject unknown fields on a write. Cap the JSON body size in the parser. A route that reads req.body with no schema is a review.

Auth and errors

A route that changes data has auth middleware. Do not check auth only in the UI. After auth, check that the resource belongs to the caller. A client-supplied user id is not identity.

The error middleware has four arguments and sits last. It logs the error and sends a status and a short body. It does not send a stack in production. Headers are not written twice.

Security and tests

helmet or the project's header middleware stays enabled. CORS lists origins. Do not reflect any Origin with credentials. Rate-limit the login route the project already protects.

A test hits the route with supertest or the project's client. Cover no token, a bad body, and a body larger than the limit if you changed the limit. Run the test script. Record the output.

Read the full file on GitHub · 95 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.

  1. today First seen · 95 lines · 0 tokens per session scan A d41eb4a68cb4

Subscribe to this mod's changes

express-rules is a cursor rule published in the GitHub repository beel-collab/presets.dev (3 stars, last pushed yesterday), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 911 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 2026-11-13.

Related

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