openapi-spec-generation

What this skill does

# OpenAPI Spec Generation

Comprehensive patterns for creating, maintaining, and validating OpenAPI 3.1 specifications for RESTful APIs.

## When to Use This Skill

- Creating API documentation from scratch
- Generating OpenAPI specs from existing code
- Designing API contracts (design-first approach)
- Validating API implementations against specs
- Generating client SDKs from specs
- Setting up API documentation portals

## Core Concepts

### 1. OpenAPI 3.1 Structure

```yaml
openapi: 3.1.0
info:
  title: API Title
  version: 1.0.0
servers:
  - url: https://api.example.com/v1
paths:
  /resources:
    get: ...
components:
  schemas: ...
  securitySchemes: ...
```

### 2. Design Approaches

| Approach         | Description                  | Best For            |
| ---------------- | ---------------------------- | ------------------- |
| **Design-First** | Write spec before code       | New APIs, contracts |
| **Code-First**   | Generate spec from code      | Existing APIs       |
| **Hybrid**       | Annotate code, generate spec | Evolving APIs       |

## Templates

### Template 1: Complete API Specification

```yaml
openapi: 3.1.0
info:
  title: User Management API
  description: |
    API for managing users and their profiles.

    ## Authentication
    All endpoints require Bearer token authentication.

    ## Rate Limiting
    - 1000 requests per minute for standard tier
    - 10000 requests per minute for enterprise tier
  version: 2.0.0
  contact:
    name: API Support
    email: [email protected]
    url: https://docs.example.com
  license:
    name: MIT
    url: https://opensource.org/licenses/MIT

servers:
  - url: https://api.example.com/v2
    description: Production
  - url: https://staging-api.example.com/v2
    description: Staging
  - url: http://localhost:3000/v2
    description: Local development

tags:
  - name: Users
    description: User management operations
  - name: Profiles
    description: User profile operations
  - name: Admin
    description: Administrative operations

paths:
  /users:
    get:
      operationId: listUsers
      summary: List all users
      description: Returns a paginated list of users with optional filtering.
      tags:
        - Users
      parameters:
        - $ref: "#/components/parameters/PageParam"
        - $ref: "#/components/parameters/LimitParam"
        - name: status
          in: query
          description: Filter by user status
          schema:
            $ref: "#/components/schemas/UserStatus"
        - name: search
          in: query
          description: Search by name or email
          schema:
            type: string
            minLength: 2
            maxLength: 100
      responses:
        "200":
          description: Successful response
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/UserListResponse"
              examples:
                default:
                  $ref: "#/components/examples/UserListExample"
        "400":
          $ref: "#/components/responses/BadRequest"
        "401":
          $ref: "#/components/responses/Unauthorized"
        "429":
          $ref: "#/components/responses/RateLimited"
      security:
        - bearerAuth: []

    post:
      operationId: createUser
      summary: Create a new user
      description: Creates a new user account and sends welcome email.
      tags:
        - Users
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/CreateUserRequest"
            examples:
              standard:
                summary: Standard user
                value:
                  email: [email protected]
                  name: John Doe
                  role: user
              admin:
                summary: Admin user
                value:
                  email: [email protected]
                  name: Admin User
                  role: admin
      responses:
        "201":
          description: User created successfully
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/User"
          headers:
            Location:
              description: URL of created user
              schema:
                type: string
                format: uri
        "400":
          $ref: "#/components/responses/BadRequest"
        "409":
          description: Email already exists
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/Error"
      security:
        - bearerAuth: []

  /users/{userId}:
    parameters:
      - $ref: "#/components/parameters/UserIdParam"

    get:
      operationId: getUser
      summary: Get user by ID
      tags:
        - Users
      responses:
        "200":
          description: Successful response
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/User"
        "404":
          $ref: "#/components/responses/NotFound"
      security:
        - bearerAuth: []

    patch:
      operationId: updateUser
      summary: Update user
      tags:
        - Users
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/UpdateUserRequest"
      responses:
        "200":
          description: User updated
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/User"
        "400":
          $ref: "#/components/responses/BadRequest"
        "404":
          $ref: "#/components/responses/NotFound"
      security:
        - bearerAuth: []

    delete:
      operationId: deleteUser
      summary: Delete user
      tags:
        - Users
        - Admin
      responses:
        "204":
          description: User deleted
        "404":
          $ref: "#/components/responses/NotFound"
      security:
        - bearerAuth: []
        - apiKey: []

components:
  schemas:
    User:
      type: object
      required:
        - id
        - email
        - name
        - status
        - createdAt
      properties:
        id:
          type: string
          format: uuid
          readOnly: true
          description: Unique user identifier
        email:
          type: string
          format: email
          description: User email address
        name:
          type: string
          minLength: 1
          maxLength: 100
          description: User display name
        status:
          $ref: "#/components/schemas/UserStatus"
        role:
          type: string
          enum: [user, moderator, admin]
          default: user
        avatar:
          type: string
          format: uri
          nullable: true
        metadata:
          type: object
          additionalProperties: true
          description: Custom metadata
        createdAt:
          type: string
          format: date-time
          readOnly: true
        updatedAt:
          type: string
          format: date-time
          readOnly: true

    UserStatus:
      type: string
      enum: [active, inactive, suspended, pending]
      description: User account status

    CreateUserRequest:
      type: object
      required:
        - email
        - name
      properties:
        email:
          type: string
          format: email
        name:
          type: string
          minLength: 1
          maxLength: 100
        role:
          type: string
          enum: [user, moderator, admin]
          default: user
        metadata:
          type: object
          additionalProperties: true

    UpdateUserRequest:
      type: object
      minProperties: 1
      properties:
        name:
          type: string
          minLength: 1
          maxLength: 100
        status:
          $ref: "#/components/schemas/UserStatus"
        role:
          type: str