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

branga breow — Mon, 24 Aug 2026 07:48:51 +0000

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/

DEV Community: branga breow

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