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.