Prompt Libraries & Skill Packs

caveman

free

Open-source skill that makes AI coding agents answer in terse caveman speak, cutting output tokens by 65% on average (22-87% by task) while keeping code, commands, and error strings byte-for-byte exact. Six intensity levels from lite to classical-Chinese wenyan. Works across Claude Code, Cursor, Windsurf, Cline, Gemini CLI, Copilot, and 30+ agents. 86.9k GitHub stars, MIT license, no telemetry. Note: compresses output tokens only; the skill adds roughly 1-1.5k input tokens per turn, so whole-session savings run smaller than the headline.

superpowers

free

Open-source agentic skills framework and software-development methodology by Jesse Vincent (obra). It registers a single SessionStart hook that makes a library of composable skills discoverable, then lets the agent run structured workflows: brainstorming, planning, test-driven development, subagent code review, and git-worktree isolation. Passive by design, it does not intercept prompts or override native plan mode, so it coexists with GitHub Spec Kit and Claude Code plan mode rather than replacing them. Works across Claude Code, Cursor, Codex, Copilot CLI, and 10+ agents. 250k+ GitHub stars, MIT license, no prompt or project data collected.

design.md

free

DESIGN.md is a format specification from Google Labs for describing a visual identity to coding agents. It pairs machine-readable design tokens (YAML front matter) with human-readable design rationale (Markdown prose), giving agents a persistent, structured understanding of your design system. Ships with an official CLI (@google/design.md) for linting (WCAG contrast, broken refs), diffing, and exporting to Tailwind v3/v4 or DTCG. Still in alpha.

obsidian skills

free

Official collection of Agent Skills for Obsidian, created by CEO Steph Ango (kepano). Teaches AI agents how to work with Obsidian Markdown (wikilinks, callouts, frontmatter), Bases databases, JSON Canvas whiteboards, the Obsidian CLI, and Defuddle web extraction. Compatible with Claude Code, Codex, and any skills-compatible agent. 13.9k+ GitHub stars.

agents.md

free

AGENTS.md is an open format standard for documenting instructions that AI coding agents need to work on software projects. Think of it as a README for agents: a dedicated, predictable place for setup commands, code style, testing instructions, and project conventions. Stewarded by the Agentic AI Foundation under the Linux Foundation, it is used by 60,000+ open-source projects.