Rendering an OpenAPI spec into browsable, testable documentation is well-documented, mechanical work — several open-source tools already do most of it, the same territory as this register's ReadMe case.
Build it
Effort: a weekendRunning cost: $0/mo to start
Why CanICodeThis says Build it
Parsing an OpenAPI/Swagger spec and rendering it as browsable documentation is a solved, well-documented pattern
An interactive 'try it' panel sending a real request is a bounded integration
Versioned docs (v1 vs v2) are straightforward content organization
The parts that'll cause problems
A visual editor for writing docs alongside the spec, not just auto-generating from it, is real additional tooling
Custom domains and white-labeled branding at scale is a real multi-tenancy feature
Analytics on which endpoints developers actually use needs event tracking layered on top
How I'd build this
frontend
Astro or Next.js
hosting
Cloudflare Pages
MVP scope
Parse an OpenAPI spec and render browsable docs
An interactive 'try it' panel sending real requests
Support for versioned docs
Postpone to v2
A visual doc-writing editor
White-labeled custom domains
Endpoint usage analytics
What it actually costs to build
AI agent — with a subscription (Claude Pro/Max, Cursor, etc.)
$0 marginal
AI agent — pay-per-use API, no subscription
$43–$86 one-time
Hosting, once it's running
$0/mo (free tier)
Domain name, if you want your own
~$12/yr
Existing tools solving a similar problem typically run $19–$99/mo — see how they compare below.
The build prompt
Build me an API documentation site, genuinely achievable using an existing renderer:
1. Parse an OpenAPI spec using an existing rendering library (Redoc or Swagger UI handle most of the parsing and layout for you).
2. Render endpoints, parameters, and example requests/responses from that parsed spec.
3. An interactive 'try it' panel that sends a real request from the docs page.
4. Support versioned docs (v1 vs v2) as separate parsed specs.
That's a real, complete API documentation site. Out of scope: a visual editor for writing docs alongside the spec, real additional tooling beyond auto-generation, and endpoint usage analytics, which needs event tracking layered on top of the docs themselves.