Web service, planned and built by me
Daesin (대신)
Describe your situation or upload a screenshot, and AI sets out the documents you need and your next steps.
What it does
It covers refunds, cancellations and complaints, through to moving house and leaving a job.
How it was built
I made the plan, the screens and the server myself.
Project notes
Real screens
Introduction
A web service for tedious errands such as refunds, cancellations and complaints. Describe the situation or upload a screenshot, and AI sets out the documents, contacts and next steps, then tracks the case until it's done.
Purpose
Turn everyday errands that are a hassle to handle alone into step-by-step tasks and documents.
Main features
- Start from one of 12 situations, such as refunds, cancelling a subscription or getting ready to move, or describe your own and attach screenshots.
- AI lists the documents, the official websites and phone numbers, and the next steps.
- Each case has a task checklist, a progress bar and deadlines in Korean time.
- Results export as PDF, DOCX, TXT or a checklist.
- Sign-in, push notifications, and adding it to a phone's home screen like an app.
- A community board with comments, a nearby-places search, and a usage dashboard for the admin.
Technology
- Next.js 16, React 19, TypeScript
- The web app
- Tailwind CSS 4
- Styling
- Supabase
- Sign-in, database, row-level security, private file storage
- OpenAI Responses API
- Reading the situation and drafting the tasks
- pdf-lib, docx
- PDF and Word export
- Vercel
- Hosting
How it was made
- 2026-09-13: added project status, search and sorting, PDF and DOCX export, community detail pages and five guides.
- 2026-09-20: audited the service against 27 requirements, one by one, and listed what was left.
Problems and fixes
- Fixed
Problem: AI calls cost money with every use.
How it was fixed Each user has a daily limit, requests stop once the monthly budget is reached, one user's simultaneous requests are locked out, and nothing retries automatically. Costs are logged from the actual token usage.
- Fixed
Problem: After Google sign-in, users were sent back to the development address (localhost).
How it was fixed The site URL in the sign-in service (Supabase) was corrected to the real domain (2026-09-13).
- Fixed
Problem: Screenshots and records that users upload must stay private.
How it was fixed Row-level security is on for all 24 database tables, attachments go to private storage (images only, up to 5 MB), and usage logs never store the full question or any key.
See it working
- Real screenshots
The pictures above are captures of the real screens.
The daesin.online address currently shows this portfolio, so the service can only be seen in screenshots. Payments are switched off until business approval.
The screens in these demos are in Korean.
Related projects
My part and AI tools
Where AI tools were used
- The service itself also uses AI (OpenAI) to read each situation and draft the tasks.