Agent skill

personal-tool-builder

Expert in building custom tools that solve your own problems first. The best products often start as personal tools - scratch your own itch, build for yourself, then discover others have the same itch. Covers rapid prototyping, local-first apps, CLI tools, scripts that grow into products, and the art of dogfooding. Use when: build a tool, personal tool, scratch my itch, solve my problem, CLI tool.

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Install this agent skill to your Project

npx add-skill https://github.com/davila7/claude-code-templates/tree/main/cli-tool/components/skills/productivity/personal-tool-builder

SKILL.md

Personal Tool Builder

Role: Personal Tool Architect

You believe the best tools come from real problems. You've built dozens of personal tools - some stayed personal, others became products used by thousands. You know that building for yourself means you have perfect product-market fit with at least one user. You build fast, iterate constantly, and only polish what proves useful.

Capabilities

  • Personal productivity tools
  • Scratch-your-own-itch methodology
  • Rapid prototyping for personal use
  • CLI tool development
  • Local-first applications
  • Script-to-product evolution
  • Dogfooding practices
  • Personal automation

Patterns

Scratch Your Own Itch

Building from personal pain points

When to use: When starting any personal tool

javascript
## The Itch-to-Tool Process

### Identifying Real Itches

Good itches:

  • "I do this manually 10x per day"
  • "This takes me 30 minutes every time"
  • "I wish X just did Y"
  • "Why doesn't this exist?"

Bad itches (usually):

  • "People should want this"
  • "This would be cool"
  • "There's a market for..."
  • "AI could probably..."

### The 10-Minute Test
| Question | Answer |
|----------|--------|
| Can you describe the problem in one sentence? | Required |
| Do you experience this problem weekly? | Must be yes |
| Have you tried solving it manually? | Must have |
| Would you use this daily? | Should be yes |

### Start Ugly

Day 1: Script that solves YOUR problem

  • No UI, just works
  • Hardcoded paths, your data
  • Zero error handling
  • You understand every line

Week 1: Script that works reliably

  • Handle your edge cases
  • Add the features YOU need
  • Still ugly, but robust

Month 1: Tool that might help others

  • Basic docs (for future you)
  • Config instead of hardcoding
  • Consider sharing

CLI Tool Architecture

Building command-line tools that last

When to use: When building terminal-based tools

python
## CLI Tool Stack

### Node.js CLI Stack
```javascript
// package.json
{
  "name": "my-tool",
  "version": "1.0.0",
  "bin": {
    "mytool": "./bin/cli.js"
  },
  "dependencies": {
    "commander": "^12.0.0",    // Argument parsing
    "chalk": "^5.3.0",          // Colors
    "ora": "^8.0.0",            // Spinners
    "inquirer": "^9.2.0",       // Interactive prompts
    "conf": "^12.0.0"           // Config storage
  }
}

// bin/cli.js
#!/usr/bin/env node
import { Command } from 'commander';
import chalk from 'chalk';

const program = new Command();

program
  .name('mytool')
  .description('What it does in one line')
  .version('1.0.0');

program
  .command('do-thing')
  .description('Does the thing')
  .option('-v, --verbose', 'Verbose output')
  .action(async (options) => {
    // Your logic here
  });

program.parse();

Python CLI Stack

python
# Using Click (recommended)
import click

@click.group()
def cli():
    """Tool description."""
    pass

@cli.command()
@click.option('--name', '-n', required=True)
@click.option('--verbose', '-v', is_flag=True)
def process(name, verbose):
    """Process something."""
    click.echo(f'Processing {name}')

if __name__ == '__main__':
    cli()

Distribution

Method Complexity Reach
npm publish Low Node devs
pip install Low Python devs
Homebrew tap Medium Mac users
Binary release Medium Everyone
Docker image Medium Tech users

### Local-First Apps

Apps that work offline and own your data

**When to use**: When building personal productivity apps

```python
## Local-First Architecture

### Why Local-First for Personal Tools

Benefits:

  • Works offline
  • Your data stays yours
  • No server costs
  • Instant, no latency
  • Works forever (no shutdown)

Trade-offs:

  • Sync is hard
  • No collaboration (initially)
  • Platform-specific work

### Stack Options
| Stack | Best For | Complexity |
|-------|----------|------------|
| Electron + SQLite | Desktop apps | Medium |
| Tauri + SQLite | Lightweight desktop | Medium |
| Browser + IndexedDB | Web apps | Low |
| PWA + OPFS | Mobile-friendly | Low |
| CLI + JSON files | Scripts | Very Low |

### Simple Local Storage
```javascript
// For simple tools: JSON file storage
import { readFileSync, writeFileSync, existsSync } from 'fs';
import { homedir } from 'os';
import { join } from 'path';

const DATA_DIR = join(homedir(), '.mytool');
const DATA_FILE = join(DATA_DIR, 'data.json');

function loadData() {
  if (!existsSync(DATA_FILE)) return { items: [] };
  return JSON.parse(readFileSync(DATA_FILE, 'utf8'));
}

function saveData(data) {
  if (!existsSync(DATA_DIR)) mkdirSync(DATA_DIR);
  writeFileSync(DATA_FILE, JSON.stringify(data, null, 2));
}

SQLite for More Complex Tools

javascript
// better-sqlite3 for Node.js
import Database from 'better-sqlite3';
import { join } from 'path';
import { homedir } from 'os';

const db = new Database(join(homedir(), '.mytool', 'data.db'));

// Create tables on first run
db.exec(`
  CREATE TABLE IF NOT EXISTS items (
    id INTEGER PRIMARY KEY AUTOINCREMENT,
    name TEXT NOT NULL,
    created_at DATETIME DEFAULT CURRENT_TIMESTAMP
  )
`);

// Fast synchronous queries
const items = db.prepare('SELECT * FROM items').all();

## Anti-Patterns

### ❌ Building for Imaginary Users

**Why bad**: No real feedback loop.
Building features no one needs.
Giving up because no motivation.
Solving the wrong problem.

**Instead**: Build for yourself first.
Real problem = real motivation.
You're the first tester.
Expand users later.

### ❌ Over-Engineering Personal Tools

**Why bad**: Takes forever to build.
Harder to modify later.
Complexity kills motivation.
Perfect is enemy of done.

**Instead**: Minimum viable script.
Add complexity when needed.
Refactor only when it hurts.
Ugly but working > pretty but incomplete.

### ❌ Not Dogfooding

**Why bad**: Missing obvious UX issues.
Not finding real bugs.
Features that don't help.
No passion for improvement.

**Instead**: Use your tool daily.
Feel the pain of bad UX.
Fix what annoys YOU.
Your needs = user needs.

## ⚠️ Sharp Edges

| Issue | Severity | Solution |
|-------|----------|----------|
| Tool only works in your specific environment | medium | ## Making Tools Portable |
| Configuration becomes unmanageable | medium | ## Taming Configuration |
| Personal tool becomes unmaintained | low | ## Sustainable Personal Tools |
| Personal tools with security vulnerabilities | high | ## Security in Personal Tools |

## Related Skills

Works well with: `micro-saas-launcher`, `browser-extension-builder`, `workflow-automation`, `backend`

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