> For the complete documentation index, see [llms.txt](https://program.hackyourfuture.dk/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://program.hackyourfuture.dk/course-content/backend/node/week2/session-materials/openapi-basics.md).

# 7. OpenAPI Basics

This file supports the OpenAPI/Swagger segment of Week 2.

## Explain the role of OpenAPI

* OpenAPI is a **contract** for your HTTP API.
* It describes:
  * Which paths and methods exist.
  * What parameters and request bodies they accept.
  * What responses (status codes and schemas) they return.
* Tools can use it to:
  * Generate documentation.
  * Generate client/server code.
  * Validate requests and responses.

## Minimal example for `GET /api/snippets`

Use a concise YAML snippet in the session:

```yaml
paths:
  /api/snippets:
    get:
      summary: List public code snippets
      responses:
        "200":
          description: List of snippets
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: "#/components/schemas/Snippet"
        "500":
          description: Server error
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Error"

components:
  schemas:
    Snippet:
      type: object
      properties:
        id:
          type: integer
        title:
          type: string
        contents:
          type: string
    Error:
      type: object
      properties:
        error:
          type: string
```

You do not have to cover the full specification. Focus on:

* Paths and operations.
* Response status codes and bodies.
* A shared `Error` schema that matches what trainees implement in code.


---

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