What is json-api-mock-generator?

The JSON API Mock Generator is a specialized Claude skill designed to accelerate software development by creating production-realistic JSON response files. It automates the generation of complex, nested data structures with accurate data types, UUIDs, and ISO-8601 timestamps, allowing developers to simulate backend endpoints for testing, prototyping, and frontend integration without the need for a functional backend.

When should I use json-api-mock-generator?

json-api-mock-generator is useful in the following scenarios: • Frontend Prototyping: Rapidly generate mock API responses for new features to build and style UI components before the actual backend services are developed. • Automated Testing and QA: Create consistent, valid, and schema-compliant JSON datasets to populate test environments and verify application logic across various data states. • API Design and Documentation: Visualize and refine RESTful API response structures, including standard data wrappers, pagination metadata, and relationship mapping for stakeholder review. • Edge Case and Error Handling: Generate specific JSON files for error responses (e.g., 404 Not Found, 500 Internal Server Error) to test how the application handles API failures. • Large Dataset Simulation: Configure record counts to generate bulk mock data for performance testing and verifying pagination or infinite scroll functionality.

name	json-api-mock-generator
description	Generate realistic JSON API mock response files with proper data types, nested structures, and configurable record counts. Triggers on "create mock API response", "generate JSON mock data", "fake API data for", "mock endpoint response".

JSON API Mock Generator

Generate production-realistic JSON API mock response files for development, testing, and prototyping.

Output Requirements

File Output: .json files with valid JSON structure Naming Convention: mock-{resource}-{endpoint}.json (e.g., mock-users-list.json)

When Invoked

Immediately generate a complete, valid JSON file. Ask no clarifying questions unless the domain is completely ambiguous.

Default Behavior

If minimal context provided, generate:

10 records for list endpoints
Realistic fake data (names, emails, dates, IDs)
Proper data types (strings, numbers, booleans, arrays, nested objects)
RESTful response wrapper structure

JSON Structure Patterns

List Endpoint Response

{
  "data": [...],
  "meta": {
    "total": 100,
    "page": 1,
    "per_page": 10,
    "total_pages": 10
  },
  "links": {
    "self": "/api/v1/resource?page=1",
    "next": "/api/v1/resource?page=2",
    "last": "/api/v1/resource?page=10"
  }
}

Single Resource Response

{
  "data": {
    "id": "uuid-here",
    "type": "resource_name",
    "attributes": {...},
    "relationships": {...}
  }
}

Error Response

{
  "error": {
    "code": "ERROR_CODE",
    "message": "Human readable message",
    "details": [...],
    "timestamp": "ISO-8601"
  }
}

Data Generation Rules

IDs

Use UUIDs for primary keys: "id": "550e8400-e29b-41d4-a716-446655440000"
Use sequential integers only if specified: "id": 1

Timestamps

ISO 8601 format: "2024-01-15T09:30:00Z"
Include created_at, updated_at for resources

Names and Text

Use realistic but clearly fake names: "Jane Smith", "Acme Corp"
Vary lengths appropriately
No lorem ipsum unless specifically for content fields

Numbers

Currency: integers in cents "amount": 9999 (represents $99.99)
Percentages: decimals "rate": 0.15
Counts: integers "quantity": 5

Relationships

Use consistent IDs across related resources
Include both ID references and nested objects where appropriate

Domain-Specific Patterns

E-commerce

{
  "id": "prod_abc123",
  "name": "Wireless Bluetooth Headphones",
  "sku": "WBH-001-BLK",
  "price": 7999,
  "currency": "USD",
  "inventory": {
    "quantity": 150,
    "warehouse": "US-WEST-01"
  },
  "images": [
    {"url": "https://cdn.example.com/products/wbh-001-1.jpg", "alt": "Front view"}
  ]
}

User/Auth

{
  "id": "usr_123abc",
  "email": "jane.smith@example.com",
  "username": "janesmith",
  "profile": {
    "first_name": "Jane",
    "last_name": "Smith",
    "avatar_url": "https://cdn.example.com/avatars/123.jpg"
  },
  "roles": ["user", "admin"],
  "verified": true,
  "created_at": "2024-01-15T09:30:00Z"
}

SaaS/Subscription

{
  "id": "sub_xyz789",
  "customer_id": "cus_abc123",
  "plan": {
    "id": "plan_pro",
    "name": "Professional",
    "amount": 4999,
    "interval": "month"
  },
  "status": "active",
  "current_period_start": "2024-01-01T00:00:00Z",
  "current_period_end": "2024-02-01T00:00:00Z"
}

Validation Checklist

Before outputting, verify:

Valid JSON (parseable)
Consistent data types throughout
IDs are unique within the file
Timestamps are valid ISO 8601
No trailing commas
Proper null handling (not "null" strings)
Arrays are properly bracketed
Nested objects are complete

Example Invocations

Prompt: "Create mock API response for a blog posts endpoint" Output: Complete mock-posts-list.json with 10 realistic blog posts including title, content, author, tags, dates, view counts.

Prompt: "Generate fake user data JSON for 25 users with addresses" Output: Complete mock-users-list.json with 25 users including nested address objects.

Prompt: "Mock API error response for 404 not found" Output: Complete mock-error-404.json with proper error structure.

json-api-mock-generator

When & Why to Use This Skill

Use Cases