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4 CLI Tools Every Developer Needs (That You've Never Heard Of)

#devtools #cli #opensource #productivity

You know that moment where you lose 3 minutes to something stupid?

EADDRINUSE. A stack trace you have to manually paste into ChatGPT. A mysterious function nobody documented. A code review that can't happen because it's 2am.

Individually, these are minor. Collectively, they steal 60+ hours a year from your workflow.

I've been using 4 CLI tools that each solve one of these problems. They're all npx-ready — you can try them in the next 30 seconds without installing anything.

1. 🛡️ portguard — Kill EADDRINUSE Instantly

The problem everyone pretends doesn't bother them:

Error: listen EADDRINUSE: address already in use :::3000
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Every time this happens, you do the same dance:

lsof -i :3000          # wait for it...
# squint at the output, find the PID
kill -9 12345           # hope you killed the right one
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It's 30 seconds. But it happens 3-5 times a day during active development.

The fix:

npx @mj-muin/portguard kill 3000
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Done. One command. No PID hunting, no wrong-process anxiety.

The real power move — add it to package.json:

{
  "scripts": {
    "predev": "npx @mj-muin/portguard kill 3000 --silent",
    "dev": "next dev"
  }
}
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Now port conflicts literally can't happen. Your npm run dev cleans up before starting.

No API key. No config. No dependencies drama. This is the tool I recommend first because it costs you nothing to try.

📦 npmjs.com/package/@mj-muin/portguard

2. 🔥 roast — Gordon Ramsay for Your Code

The 2am problem:

You're working solo. Or your team's in a different timezone. You know this function is bad but can't articulate why. There's nobody to review your code.

What you'd normally do:

  • Paste code into ChatGPT (loses file context)
  • Write a PR and wait 12 hours (kills momentum)
  • Ship it and hope (we all know how this ends)

What you do instead:

npx @mj-muin/roast src/utils.js
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🔥 ROAST REPORT: src/utils.js
━━━━━━━━━━━━━━━━━━━━━━━━━━━━━

🤦 Line 12-89: This function is 77 lines long.
   That's not a function, that's a short story.
   → Extract the validation logic into its own function.

🐛 Line 34: You're catching errors and doing nothing.
   catch(e) {} is not error handling, it's error hiding.
   → At minimum, log it. Better: handle it or let it propagate.

💀 Line 56: == null vs === null
   I see you like to live dangerously.
   → Use strict equality. Always.

📊 Overall: 4/10 — Functional but fragile.
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It's not just criticism — it's education. Every issue comes with why it's bad and how to fix it. Like a senior dev who's grumpy but helpful.

When this saves your neck:

  • Solo dev with nobody to review
  • Onboarding yourself onto a new codebase
  • Pre-PR sanity check before bothering your team
  • Learning — the roast explains patterns you might not know

📦 npmjs.com/package/@mj-muin/roast (requires ANTHROPIC_API_KEY)

3. 🏺 git-why — Understand Legacy Code Without Bothering Anyone

The onboarding problem:

You join a project. You see this:

// DO NOT REMOVE — breaks production
const delay = await sleep(2100);
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git blame tells you Sarah wrote it 18 months ago. Sarah left the company 6 months ago. The commit message says "fix."

Helpful.

The real question isn't who wrote it or when — it's why.

npx @mj-muin/git-why src/auth.js
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git-why reads git history — commits, diffs, messages across the file's lifetime — and uses AI to reconstruct the intent behind changes.

It might tell you: "This 2.1-second delay was added after commit a3f7c2d because the auth provider rate-limits requests under 2 seconds apart. See PR #142 for the incident report."

Now you know not to remove it. Or that you can remove it if you switch auth providers.

Where this is invaluable:

  • Onboarding: New team member ramps up in hours, not weeks
  • Refactoring: Know what you'll break before you break it
  • Code archaeology: That // HACK comment from 2019 finally makes sense
  • Due diligence: Evaluating an acquired codebase

📦 npmjs.com/package/@mj-muin/git-why (requires ANTHROPIC_API_KEY)

4. 💥 oops — Pipe Errors Directly to AI

The context-switching tax:

Your app crashes. You get a stack trace. Here's what happens next:

  1. Copy the error
  2. Open browser
  3. Navigate to ChatGPT
  4. Paste error
  5. Wait for response
  6. Context-switch back to terminal
  7. Realize you forgot to include the file contents
  8. Repeat steps 1-6

That's not debugging. That's a scavenger hunt.

The fix:

node app.js 2>&1 | oops
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That's it. The full stderr — stack trace, file paths, line numbers, everything — goes directly to AI analysis. The response appears right in your terminal.

$ node server.js 2>&1 | oops

🔍 Analyzing error...

❌ TypeError: Cannot read properties of undefined (reading 'id')
   at /app/src/handlers/user.js:42

💡 The user object is undefined because the auth middleware
   isn't running before this route handler.

🔧 Fix: Add auth middleware before the route:
   app.get('/profile', authMiddleware, profileHandler)
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No tab switching. No copy-paste. No losing your mental context. The answer shows up where you're already working.

Works with anything that outputs to stderr:

python train.py 2>&1 | oops
cargo build 2>&1 | oops
go run main.go 2>&1 | oops
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📦 npmjs.com/package/@mj-muin/oops-cli (requires ANTHROPIC_API_KEY)

Try Them Right Now 

# Zero config — works immediately
npx @mj-muin/portguard list

# AI-powered (one-time setup)
export ANTHROPIC_API_KEY=sk-ant-...

npx @mj-muin/roast src/index.js
npx @mj-muin/git-why src/auth.js
node app.js 2>&1 | oops
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Three of the four need an Anthropic API key. portguard needs absolutely nothing.

All four are open source, MIT licensed, and on npm under @mj-muin.

The Backstory

These tools weren't built by a product team with a roadmap. They were built by an AI COO — literally an AI agent running operations for a one-person company — over the course of 52 days.

If you're curious about what it's like to run a company where the COO is a language model and the tools get built by sub-agents, I wrote about the honest numbers (711 commits, 0 users, $0 revenue) in the first post of this series:

👉 Day 52: Building vs Shipping — Why We Had 711 Commits and 0 Users

What's your most annoying daily dev friction? I'm always looking for the next 30-second problem to automate away. 👇

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