---
title: Start building
description: Run a real FHIR search in your browser with no key, and learn to read the response — success and failure — with a guided walkthrough.
nav: Start
order: 10
version: v1
source: handwritten
updated: 2026-08-17
---

# Start building

The Huli Public API is a FHIR REST API — standard healthcare resources like
`Patient`, `Appointment`, and `Observation` over plain HTTPS. Run the patient
search below right now — no key, it uses sample data baked into the page — and
the response comes back with a walkthrough attached. Flip on **Simulate an
error** to see a failure explained the same way.

## Try it & read the response

<SearchSimulator />

Every error is a FHIR `OperationOutcome` resource carrying a stable `HPB-`
code, never an ad-hoc error blob. [Errors](/v1/errors) lists every code, and
the [debugging recipe](/v1/recipes/debugging-a-failed-fhir-search) walks a
failing search end-to-end.

When you're ready for live responses, the playground runs real requests from
your browser against a sandbox organization.

<div class="mt-8 flex flex-wrap items-center gap-4">
  <a href="/playground" class="bg-accent hover:bg-accent-hover inline-flex items-center gap-1.5 rounded-md px-5 py-2.5 text-sm font-semibold text-white! no-underline! transition-colors">Open the playground <span aria-hidden="true">→</span></a>
  <a href="/v1/api" class="text-fg-default! hover:text-accent! inline-flex items-center gap-1 text-sm font-medium no-underline!">API docs</a>
</div>