What is Swagger used for?

Swagger (now OpenAPI Specification) is used for describing, documenting, and visualizing RESTful APIs. It allows developers, testers, and API consumers to understand the functionality of a service without access to the source code.

Main functions:

1. Documentation: Automatic creation of interactive API documentation.
2. Development: Assists in API development by providing a clear contract definition.
3. Testing: Swagger UI allows testing API endpoints directly from the browser.
4. Code Generation: You can generate client code (SDK) or server stubs based on the OpenAPI specification.
5. Design: Can be used as a tool for designing APIs before coding (Design-First Approach).

Example of a specification fragment in YAML format:

# Short description of the API
openapi: 3.0.0
info:
  title: My Test API
  version: 1.0.0
paths:
  /items:
    get:
      summary: Get a list of all items
      responses:
        '200':
          description: List of items successfully retrieved
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Item'
components:
  schemas:
    Item:
      type: object
      properties:
        id:
          type: integer
          format: int64
        name:
          type: string

This ensures consistency among different parties involved in API development and usage.