How I Built 5 Developer Tool APIs on a Raspberry Pi (And Listed Them on RapidAPI)

#ai #webdev #productivity #api

This is a writeup of how I built and launched a small API hub — what worked, what didn't, and the tech stack behind it.

The Problem
As developers, we use the same tools over and over: prompt optimization, JSON validation, text analysis. These are small, repeatable tasks that don't need a full SaaS — they just need a reliable API endpoint.

The Stack
Runtime: Python FastAPI in a Docker container
Host: Raspberry Pi 4 (8GB) in my garage
Tunnel: Cloudflare Tunnel (zero open ports on router)
Domain: kowhaigoods.com via GitHub Pages
Marketplace: RapidAPI Hub

The 5 Endpoints
AI Prompt Optimizer
POST /prompt-optimizer/optimize

Send a raw prompt like "write me a blog post about dogs" and get back a structured prompt with:
Role definition ("You are an expert content writer...")
Task specification
Constraints
Output format guidance

JSON Schema Validator
POST /json-tools/validate

Validates JSON data against a schema — useful for CI/CD pipelines and form validation.

3-4. JSON Formatter & Converter
Format/beautify JSON with custom indentation, and convert between JSON ↔ CSV ↔ YAML.

Text Readability & SEO Analyzer
POST /text-analyzer/analyze

Returns readability scores (Flesch-Kincaid, Gunning Fog, SMOG), SEO metrics (word count, keyword density, sentence structure), and improvement suggestions.

What Worked
Free tier is essential. 100 requests/month free. Nobody pays $9.99/mo for an API they haven't tested.
SEO + FAQ schema drives organic traffic. Blog posts with FAQPage JSON-LD schema show up in Google's answer snippets.
Cloudflare Tunnel is perfect for homelab hosting. No port forwarding, automatic SSL, DDoS protection built in.

What Didn't Work (1/2)
Reddit r/programming — strict anti-self-promo, post was removed. Use r/SideProject instead.
Stack Overflow — any mention of your own product gets flagged. Don't bother.
Direct cold outreach to devs — low response rate. Inbound (SEO + marketplace) works better.

Try It
Free tier: https://rapidapi.com/kowhai-text-utilities
Full API docs: https://kowhaigoods.com/api-docs.html
Blog: https://kowhaigoods.com/

Top comments (1)

Amit Feldman • Aug 24

Raspberry Pi + Cloudflare Tunnel + RapidAPI is a great zero-budget stack — nice writeup, especially the honest "what didn't work" framing.

Ran a quick public check of kowhaigoods.com while reading (response headers only, nothing a first-time visitor's browser doesn't see):

The plain-http version serves a full 200 with no redirect to https — so the TLS you have never protects anyone who hits port 80 first. One Redirect Rule fixes it.
All six baseline security headers are missing on the https response — Strict-Transport-Security, Content-Security-Policy, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy. HSTS matters most once the redirect lands; CSP is the one that actually limits what injected content can do.
Access-Control-Allow-Origin: * rides on the page routes — harmless on a static landing today, but it's the kind of header that gets forgotten and then matters the day you point an API or auth flow at that domain.

The catch: GitHub Pages can't set custom headers at the origin — but you already have Cloudflare in your stack for the tunnel, so the fix is close at hand. Route the landing through Cloudflare too (free tier), then one Transform Rule for the header block plus one Redirect Rule for http→https is roughly twenty minutes of dashboard work, and CSP can roll out report-only first so nothing breaks.

None of it blocks the launch — but for a product asking devs to wire paid API calls into their apps, the header layer is the first thing a technical buyer checks. Happy to re-run the check free any time.