---
title: 'CodeSystem (FHIR R4)'
description: 'FHIR R4 CodeSystem resource.'
nav: 'API / R4 / CodeSystem'
order: 210
version: v1
fhir: r4
source: generated
updated: '2026-09-23'
---

# CodeSystem (FHIR R4)

<FhirResourceHeader fhir="r4" slug="codesystem" />

FHIR R4 CodeSystem resource.

> This reference is generated from the canonical Huli Public API OpenAPI specification and the server's FHIR R4 CapabilityStatement — do not edit it directly.

## FHIR R4 Specification

Official spec: [CodeSystem — HL7 FHIR R4](https://hl7.org/fhir/R4/codesystem.html)

## Supported Interactions

- **read** — Read a single resource by ID (`GET /fhir/R4/{Resource}/{id}`)

<Callout variant="note">
Terminology resource. Scope is enforced per CodeSystem id by the handler (e.g. `address-source` → `system/Patient.rs`, `org-service` → `system/Appointment.rs`).
</Callout>

## Scopes

Scopes are shared across FHIR releases — the same `system/CodeSystem.*` scope grants CodeSystem access on both `/fhir/R4` and `/fhir/R5`.


## Endpoints

### Read CodeSystem

Retrieve a static Huli CodeSystem by id. Scope is enforced per-id:
  - `address-source` requires `system/Patient.rs`
  - `org-service` requires `system/Appointment.rs`

<Endpoint method="GET" path="/fhir/R4/CodeSystem/{id}" />

**Required scope:** <Scope name="system/Patient.rs" />

#### Response — 200

```json
{
  "resourceType": "CodeSystem",
  "url": "https://huli.io/fhir/CodeSystem/address-source",
  "status": "active",
  "content": "complete",
  "concept": [
    {
      "code": "mx-normativo-nom024",
      "display": "NOM-024 normative address source"
    }
  ]
}
```

#### Code Samples

:::CodeGroup

```bash {label="cURL"}
TOKEN=$(curl -s -X POST https://api.huli.ai/auth/token \
  -d "grant_type=client_credentials" \
  -d "client_assertion_type=urn:ietf:params:oauth:client-assertion-type:jwt-bearer" \
  -d "client_assertion=${CLIENT_ASSERTION}" \
  -d "scope=system/Patient.rs" \
  | jq -r .access_token)

curl -X GET https://api.huli.ai/fhir/R4/CodeSystem/${RESOURCE_ID} \
  -H "Authorization: Bearer ${TOKEN}"
```

```typescript {label="TypeScript"}
const token = process.env.HULI_ACCESS_TOKEN ?? "";

const response = await fetch(
  `https://api.huli.ai/fhir/R4/CodeSystem/${id}`,
  {
    method: "GET",
    headers: {
      "Authorization": `Bearer ${token}`,
    },

  }
);

if (!response.ok) throw new Error(`HTTP ${String(response.status)}`);
const data: unknown = await response.json();
```

```python {label="Python"}
import os
import requests

token = os.environ["HULI_ACCESS_TOKEN"]
headers = {"Authorization": f"Bearer {token}"}

resp = requests.get(
    f"https://api.huli.ai/fhir/R4/CodeSystem/{resource_id}",
    headers=headers,
)
resp.raise_for_status()
print(resp.json())
```

```java {label="Java"}
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class getCodeSystemExample {
    public static void main(String[] args) throws Exception {
        String token = System.getenv("HULI_ACCESS_TOKEN");
        String resourceId = "RESOURCE_ID";

        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.huli.ai/fhir/R4/CodeSystem/" + resourceId))
        .header("Authorization", "Bearer " + token)
        .header("Accept", "application/fhir+json")
        .method("GET", HttpRequest.BodyPublishers.noBody())
        .build();

        HttpResponse<String> response =
        client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println("status: " + response.statusCode());
        System.out.println(response.body());
    }
}
```

```go {label="Go"}
import (
    "fmt"
    "net/http"
    "os"
)

func getCodeSystemExample() {
    token := os.Getenv("HULI_ACCESS_TOKEN")
    req, _ := http.NewRequest("GET", "https://api.huli.ai/fhir/R4/CodeSystem/"+resourceID+"", nil)
    req.Header.Set("Authorization", "Bearer "+token)

    resp, err := http.DefaultClient.Do(req)
    if err != nil {
        fmt.Println("error:", err)
        return
    }
    defer resp.Body.Close()
    fmt.Println("status:", resp.Status)
}
```

:::

#### Errors

| Code | Status | Description |
|------|--------|-------------|
| [HPB-00106](/v1/errors#hpb-00106) | 401 | Authentication failed |
| [HPB-00104](/v1/errors#hpb-00104) | 403 | Insufficient scope |
| [HPB-00102](/v1/errors#hpb-00102) | 404 | Resource not found |
| [HPB-00105](/v1/errors#hpb-00105) | 429 | Rate limit exceeded |

---