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Build a REST API in Plain English

This guide builds a working JSON REST API in EPL — a programming language whose keywords are ordinary English. If you can read a sentence, you can read this API. Every snippet below is runnable; copy it, run it, and hit it with curl.

Install: pip install eplang · Try in the browser (no install): EPL Playground

The smallest possible API

Create a file api.epl:

Create WebApp called app

Route "/api/greeting" responds with
    Send json Map with message = "Hello from EPL" and status = "ok"
End

Start app on port 8000

Run it:

epl serve api.epl

Then in another terminal:

curl http://127.0.0.1:8000/api/greeting

{
  "message": "Hello from EPL",
  "status": "ok"
}

That's a complete HTTP JSON endpoint. No framework to install, no boilerplate, no decorators — Create WebApp, Route ... responds with, Send json.

Returning a list of records

A Map is EPL's key–value object (like a JSON object / Python dict). A list of maps is a JSON array of objects:

Create WebApp called app

Route "/api/users" responds with
    users = [Map with name = "Ada" and role = "admin", Map with name = "Bob" and role = "user"]
    Send json Map with data = users and count = length(users)
End

Start app on port 8000

curl http://127.0.0.1:8000/api/users

{
  "data": [
    { "name": "Ada", "role": "admin" },
    { "name": "Bob", "role": "user" }
  ],
  "count": 2
}

length(users) is a built-in — no import required.

Multiple routes and a health check

Real services expose several endpoints. Add as many Route blocks as you need:

Create WebApp called app

Route "/api/greeting" responds with
    Send json Map with message = "Hello from EPL" and status = "ok"
End

Route "/api/users" responds with
    users = [Map with name = "Ada" and role = "admin", Map with name = "Bob" and role = "user"]
    Send json Map with data = users and count = length(users)
End

Route "/health" responds with
    Send json Map with status = "healthy"
End

Start app on port 8000

A /health endpoint that returns {"status": "healthy"} is exactly what a load balancer or Kubernetes liveness probe expects.

How this compares

The same greeting endpoint in three languages:

Route "/api/greeting" responds with
    Send json Map with message = "Hello from EPL" and status = "ok"
End

@app.route("/api/greeting")
def greeting():
    return {"message": "Hello", "status": "ok"}

app.get("/api/greeting", (req, res) => {
  res.json({ message: "Hello", status: "ok" });
});

EPL reads as instructions, not symbols — which is the point. It's approachable for beginners and non-native English speakers learning to program, while still running on a real toolchain (interpreter, bytecode VM, and native compiler).

Going to production

epl serve is the development server. For production, EPL generates WSGI/ASGI adapters and deployment manifests:

pip install "eplang[server]"
epl serve api.epl --csp        # strict Content-Security-Policy
epl deploy k8s api.epl --image myapi:1.0 --tls

See the Web Guide for routing, sessions, templates, and the security model, and Deployment for packaging.

Next steps