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