How I Built a Developer Tool That Saves 10 Hours/Week

It started with a simple frustration.

I was copy-pasting JSON from an API response into a TypeScript file for the third time that day. My hands hovered over the keyboard, about to manually type out another interface with 47 fields.

Then I stopped.

"There has to be a better way."

That thought changed everything. Six months later, I had built a tool that thousands of developers now use daily. This is that story.

The Problem I Couldn't Ignore

I'm a frontend developer. Or at least, I was supposed to be.

But I spent 10-15 hours every week doing mindless data conversion tasks:

Converting JSON API responses to TypeScript interfaces

Transforming JSON data into CSV for stakeholders

Generating mock data for testing

Reformatting JSON into YAML for config files

None of this was coding. None of it was creative. It was pure mechanical work that a computer should do.

One week, I tracked my time obsessively. Here's what I found:

Monday: 2 hours converting API responses to TypeScript

Tuesday: 1.5 hours generating CSV reports from JSON

Wednesday: 45 minutes creating mock JSON data

Thursday: 2 hours debugging malformed JSON

Friday: 3 hours updating TypeScript interfaces after API changes

Total: 9 hours and 15 minutes.

Nearly a quarter of my working week. Gone. Not building features. Not solving problems. Just converting data formats.

I did the math: At my hourly rate, this was costing my company $3,700 per month. Just for me. We had a team of eight developers, all doing similar work.

That's when I decided to build something.

The First Attempt (That Failed)

My first idea was simple: a Python script.

import json

import sys



def json_to_typescript(json_data):

    # Generate TypeScript interface

    # ...yeah, this got complicated fast

I spent three evenings on it. The script worked for simple JSON, but broke on nested objects. It couldn't handle arrays properly. Optional fields confused it. Union types were impossible.

After a week, I had a 400-line Python script that worked maybe 60% of the time.

My teammate saw me struggling and said, "Why don't you just use one of those online converters?"

I Googled "JSON to TypeScript converter."

Dozens existed.

My heart sank. Why was I reinventing the wheel?

But then I tried them. One by one.

Every single tool had issues:

• Slow page loads (ads everywhere)


• Requires sign-up or payment


• Ugly interfaces from 2010


• Only handles one conversion type


• Data sent to their servers (security concern)


• No dark mode (I code at night)

They worked, technically. But none were tools I wanted to use.

That's when I realized: the opportunity wasn't in building a converter. It was in building a converter developers actually enjoy using.

Building the Right Thing

I started with a simple philosophy:

Make it so good that I'd use it myself, every single day.

Principle 1: Privacy First

Most online converters send your data to their servers. For personal projects, fine. For work with proprietary API data? Not acceptable.

I made everything run client-side in the browser. Your JSON never leaves your computer. No servers. No logs. No risk.

Principle 2: Speed Obsession

I tested every competitor. They averaged 2-3 seconds to load the page before you could even paste your JSON.

I set a goal: instant. When you visit my tool, you can immediately start pasting. No loading spinners. No ads. No unnecessary cruft.

Principle 3: Actually Beautiful

Most developer tools look like they were designed in 1995. Gray backgrounds, Times New Roman, no polish.

I spent days on the UI. Dark mode default. Clean typography. Smooth animations. It should feel like a modern app, not a legacy tool.

Principle 4: Do ONE Thing Perfectly

Instead of building a "Swiss Army knife" tool that does 50 things poorly, I focused on doing JSON conversion perfectly.

Each converter got its own page. Each one handles edge cases. Each one gives clear error messages.

Principle 5: Free Forever

I was tired of "free trials" and "upgrade to premium" upsells.

Everything is free. No ads. No premium tier. No catch.

Why? Because I built this for me, and I hate ads. If it helps other developers too, that's just a bonus.

The Build Process

I'm not a designer. I'm not a UI/UX expert. I'm just a developer who's tired of ugly tools.

But I had Tailwind CSS, Claude AI for brainstorming, and a lot of determination.

Week 1: The Core Converter

I started with JSON to TypeScript because that was my personal pain point.

The algorithm had to handle:

• Nested objects


• Arrays of objects


• Optional fields vs required fields


• Union types (when values could be multiple types)


• Date strings


• Null values

The first version took 6 hours to build. It worked on my test cases.

Then I tested it on real API responses from projects I'd worked on.

It broke on 40% of them.

Week 2-3: Edge Cases

Every day, I'd find new edge cases:

• Empty arrays (how do you infer type from []?)


• Inconsistent data (array where objects have different fields)


• Circular references


• Very deeply nested objects (10+ levels)


• Special characters in field names

Each edge case took 30-60 minutes to handle properly.

This was the unglamorous part. Not building new features. Just making the existing feature work reliably.

But this is what separates a toy from a tool. Toys work on simple examples. Tools work on real-world data.

Week 4: The Other Converters

Once JSON to TypeScript was solid, I added:

• JSON to CSV (for stakeholder reports)


• JSON to YAML (for config files)


• JSON to Python (for backend team)


• JSON to SQL (for database work)

Each converter was 3-5 days of work. Same pattern:

• Build basic version (2-3 hours)


• Test on real data (1 hour)


• Fix edge cases (2-3 days)


• Polish UI (1 day)

Week 5-6: The Unique Feature

Everyone has JSON converters. I needed something no one else had.

I discovered TOON (Token-Oriented Object Notation) - a format optimized for AI/LLM usage. JSON wastes tokens when sending data to GPT-4 or Claude because of all the quotes and braces.

TOON is 30-40% more compact. For developers making thousands of API calls to OpenAI, this translates to real cost savings.

I built a JSON to TOON converter. To my knowledge, I was the first to make it easily accessible online.

This became my differentiator.

Launch Day

I didn't do a big launch. No Product Hunt submission. No Hacker News post.

I just tweeted: "Built a tool for JSON conversion. Try it if you need to convert JSON to TypeScript: . It's free, fast, and privacy-first. Built by a developer, for developers.

If you've ever spent hours on mindless data conversion, give it a try. It might just save you 10 hours this week.

What repetitive task frustrates you daily? Maybe that's your opportunity to build something people actually want.

Drop a comment - I'd love to hear about the tools you wish existed.