Six weeks ago I had an idea. Today it’s a live product
with real users.
fynPrint reads any contract (PDF or DOCX), flags risky
clauses in plain English, and writes the negotiation email
for you.
The stack:
- Next.js 14 + TypeScript + Tailwind (App Router)
- Supabase (PostgreSQL + encryption at rest)
- Clerk for auth
- Claude Sonnet 4.6 API with zero data retention
- Stripe (credit-based pricing)
- Vercel
The hardest part – prompting Claude for consistent
structured JSON:
Getting reliable JSON output with risk scores, confidence
levels, and plain-language explanations per clause took
a lot of iteration. The key things that worked:
-
Be extremely specific about the exact JSON structure
you want. Include field names, types, and examples. -
Tell Claude explicitly what NOT to include in low-risk
clauses to reduce output tokens and speed up response time. -
Add “Return ONLY valid JSON. No markdown, no code
fences, no preamble.” at the end of every prompt –
without this you’ll get inconsistent formatting. -
For the negotiation email, pass only the selected
high-risk clauses back to Claude, not the full analysis –
keeps the second API call fast and cheap.
Pricing decision:
Went credit-based ($2.99 per analysis) instead of
subscriptions. Most freelancers don’t sign contracts every
week – a monthly subscription felt wrong for that use case.
Looking for beta testers:
If you’re a developer who freelances and signs client
contracts, I’d love your honest feedback on the analysis accuracy.
5 free credits – just sign up at fynprint and DM me.
Happy to answer questions about the architecture or
prompting approach in the comments.
