Is the Who Built This Before Me skill free?

Yes. The skill itself is free from iagochavarry/who-built-this-before-me. SkillProof publishes the install command and an independent test verdict at no cost.

What is the Who Built This Before Me SkillProof Score?

9.6/10 — installs cleanly 5/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 5/5.

How do I install Who Built This Before Me?

Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.

Can I use Who Built This Before Me with Cursor, Copilot, Gemini CLI, Codex or other AI tools?

The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.

Who Built This Before Me

Prior-art search before you build: verdict is build, fork, contribute, use, or investigate.

by iagochavarry · iagochavarry/who-built-this-before-me

Tested · Works

Install — copy the command Download source ↗

Test report

Verdict: Tested · Works
Score: 9.6/10
Tested: Jul 14, 2026
Environment: Claude Code 2.x (agent harness)
Upstream re-checked: Aug 10, 2026 · 5706393

Fed it a real idea (semantic JSON diff CLI); the vocabulary-framing step alone surfaced jd, sdiff-rs and dyff — tools a single generic search misses entirely — then forced a real verdict instead of hedging.

Scored on four weighted criteria — install, triggering, output vs. baseline, docs. How scoring works

Installs cleanly 5/5
Triggers reliably 5/5
Output vs. baseline 9/10
Docs & honesty 5/5

What Who Built This Before Me does

Runs a structured prior-art search before you sink time into a new project, library, or side hustle — generates 6-10 vocabulary framings, searches GitHub/Show HN/registries, clusters results into direct/adjacent/partial/abandoned buckets, and forces a one-line verdict instead of hedging. Triggers on "I want to build...", "is there already a...", or any idea-scoping conversation, even without an explicit research request.

How to install Who Built This Before Me

git clone https://github.com/iagochavarry/who-built-this-before-me ~/.claude/skills/who-built-this-before-me

Skills live in ~/.claude/skills/ (global) or .claude/skills/ (per-project). Restart Claude Code after installing.

Commands — how to trigger Who Built This Before Me

/who-built-this-before-me Prior-art search before you build: verdict is build, fork, contribute, use, or investigate.

It also activates on plain-language prompts like these:

I'm thinking of building a habit tracker app, does one already exist?
Before I start this side project, can you check if it's already built?
Should I build this JSON diff CLI or is there already a good one?

Frequently asked questions

Is the Who Built This Before Me skill free?: Yes. The skill itself is free from iagochavarry/who-built-this-before-me. SkillProof publishes the install command and an independent test verdict at no cost.
Does Who Built This Before Me work with Claude Code?: We tested it with Claude Code 2.x (agent harness) on Jul 14, 2026. Verdict: Tested · Works. Fed it a real idea (semantic JSON diff CLI); the vocabulary-framing step alone surfaced jd, sdiff-rs and dyff — tools a single generic search misses entirely — then forced a real verdict instead of hedging.
What is the Who Built This Before Me SkillProof Score?: 9.6/10 — installs cleanly 5/5, triggers reliably 5/5, output vs. baseline 9/10, docs & honesty 5/5.
How do I install Who Built This Before Me?: Copy the install command from this page, run it in your terminal, and restart Claude Code. Skills live in ~/.claude/skills/ (global) or .claude/skills/ inside a project.
Can I use Who Built This Before Me with Cursor, Copilot, Gemini CLI, Codex or other AI tools?: The SKILL.md format is native to Claude (Claude Code, Desktop, claude.ai). The instructions inside adapt to other assistants: Cursor rules, GitHub Copilot instructions, Windsurf rules, Custom GPTs, AGENTS.md for OpenAI Codex, and GEMINI.md for Google Gemini CLI — our conversion guides cover each, and the free converter on the tools page does the wrapping for you.