personal-tool-builder

What this skill does

# 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.

**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.

### Expertise

- Rapid prototyping
- CLI development
- Local-first architecture
- Script automation
- Problem identification
- Tool evolution

## 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

## 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

## 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

## 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();
```

### Script to Product Evolution

Growing a script into a real product

**When to use**: When a personal tool shows promise

## Evolution Path

### Stage 1: Personal Script
```
Characteristics:
- Only you use it
- Hardcoded values
- No error handling
- Works on your machine

Time: Hours to days
```

### Stage 2: Shareable Tool
```
Add:
- README explaining what it does
- Basic error messages
- Config file instead of hardcoding
- Works on similar machines

Time: Days
```

### Stage 3: Public Tool
```
Add:
- Installation instructions
- Cross-platform support
- Proper error handling
- Version numbers
- Basic tests

Time: Week or two
```

### Stage 4: Product
```
Add:
- Landing page
- Documentation site
- User support channel
- Analytics (privacy-respecting)
- Payment integration (if monetizing)

Time: Weeks to months
```

### Signs You Should Productize
| Signal | Strength |
|--------|----------|
| Others asking for it | Strong |
| You use it daily | Strong |
| Solves $100+ problem | Strong |
| Others would pay | Very strong |
| Competition exists but sucks | Strong |
| You're embarrassed by it | Actually good |

## Sharp Edges

### Tool only works in your specific environment

Severity: MEDIUM

Situation: Script fails when you try to share it

Symptoms:
- Works on my machine
- Scripts failing for others
- Path not found errors
- Command not found errors

Why this breaks:
Hardcoded absolute paths.
Relies on your installed tools.
Assumes your OS/shell.
Uses your auth tokens.

Recommended fix:

## Making Tools Portable

### Common Portability Issues
| Issue | Fix |
|-------|-----|
| Hardcoded paths | Use ~ or env vars |
| Specific shell | Declare shell in shebang |
| Missing deps | Check and prompt to install |
| Auth tokens | Use config file or env |
| OS-specific | Test on other OS or use cross-platform libs |

### Path Portability
```javascript
// Bad
const dataFile = '~/data.json';

// Good
import { homedir } from 'os';
import { join } from 'path';
const dataFile = join(homedir(), '.mytool', 'data.json');
```

### Dependency Checking
```javascript
import { execSync } from 'child_process';

function checkDep(cmd, installHint) {
  try {
    execSync(`which ${cmd}`, { stdio: 'ignore' });
  } catch {
    console.error(`Missing: ${cmd}`);
    console.error(`Install: ${installHint}`);
    process.exit(1);
  }
}