Node.js · TypeScript · Fastify

Fastify rules for Cursor

Plugin, schema and error-handling rules for Fastify APIs.

The rule

Save as .cursor/rules/fastify.mdc. Cursor picks it up on the next request.

.cursor/rules/fastify.mdc

---
description: Fastify API conventions
globs: src/**/*.ts
alwaysApply: false
---

- Organize features as Fastify plugins registered with fastify.register; use fastify-plugin only when decorators must be shared.
- Declare a JSON schema (or TypeBox/Zod type provider) for every route's body, params, querystring and response.
- Use async handlers and return values instead of calling reply.send where possible.
- Throw errors created with @fastify/error or http-errors; let the error handler format responses.
- Use fastify.log (pino), not console.log.
- Close resources in onClose hooks so tests can shut the server down cleanly.

How Cursor loads this rule

Read from the frontmatter above, per Cursor's rules documentation.

  • alwaysApply: false with globs: src/**/*.ts: attached automatically when a matching file is in context.
  • Keep the .mdc extension. A plain .md file in .cursor/rules is ignored by the rules system.
  • Prefer to generate your own? Type /create-rule in Agent and describe what you want; Cursor saves the file to .cursor/rules.
  • Team Rules come first, then Project Rules like this one, then User Rules. Earlier sources win when guidance conflicts.

Cursor rules setup guideCursor Team RulesLet Cursor run commands without asking

Using another agent too?

The same instructions work as plain Markdown in AGENTS.md, which Codex, Gemini CLI, GitHub Copilot and most other coding agents read.

AGENTS.md (section)

## Fastify

- Organize features as Fastify plugins registered with fastify.register; use fastify-plugin only when decorators must be shared.
- Declare a JSON schema (or TypeBox/Zod type provider) for every route's body, params, querystring and response.
- Use async handlers and return values instead of calling reply.send where possible.
- Throw errors created with @fastify/error or http-errors; let the error handler format responses.
- Use fastify.log (pino), not console.log.
- Close resources in onClose hooks so tests can shut the server down cleanly.

More templates

Next.js App RouterTypeScript (strict)React componentsPythonFastAPINode.js and ExpressGoRustData science notebooks and pipelinesTesting disciplineSecurity guardrails

Get Cursor rules and settings changes by email

When Cursor changes how rules, run modes or settings work, we update these templates from the docs and send a short note. One email a week at most.

Reviewed Oct 17, 2026. Written by AgentAtlas. Adapt it to your codebase before relying on it.