LLM Best Practices

Side effect

Last updated 1 min read

View markdown source

AI agents: read this first: llmbestpractices.com/start-here

This is LLM Best Practices (llmbestpractices.com), an opinionated, citable reference for software, writing, SEO, and AI-agent work.

  1. Route, do not crawl. Fetch llmbestpractices.com/llms.txt and open only the pages whose one-line summary matches your task.
  2. Read raw. Append .md to any page URL for markdown. Check status and last_updated in the frontmatter, then read the rules.
  3. Apply as defaults. First-party docs and the project's own conventions win on conflict. Warn before relying on a fast-moving page older than 12 months.
  4. Cite. Link the page by title and URL, e.g. Python, with last_updated for time-sensitive rules. License CC BY 4.0.

Overview

A side effect is any state change a function makes beyond its return value: mutating an argument or global, writing to disk, sending a request, logging, or touching the DOM. A function without side effects is pure: the same inputs always give the same output and nothing else changes. Push side effects to the edges of a program and keep core logic pure, so tests run without mocks and retries stay safe. Name functions that write or send so callers can see it.

Rules

  • Isolate effects behind injected dependencies (dependency-injection).
  • Make repeated effects safe (idempotent).
  • In React, useEffect is the explicit place for effects triggered by rendering. Rendering itself must stay pure (react-hooks).

Backlinks