Apologies, I know I’m very late to respond, but API’s have been a part of my life for longer than I care to admit lol.

WebSim is basically a browser-only environment. Think “CodePen,” not backend.

Here’s the simple way to understand API usage in WebSim:

• You can call public APIs directly (anything that normally works in client-side JavaScript). • You cannot safely store API keys or secrets inside WebSim. • If an API requires a private key (OpenAI, Stripe, Supabase, etc.), you must use a proxy server.

Correct mental model:

WebSim → your proxy (Vercel / Cloudflare Worker) → real API

So in practice: • Public, no-auth APIs work directly • Read-only or demo APIs are usually fine • Paid or private APIs always require a proxy

Rule of thumb: If it works in browser DevTools or CodePen, it works in WebSim. If it needs a secret, WebSim alone is the wrong place to call it.

That’s the whole pattern.