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Yuli Petrilli
Yuli Petrilli

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I Built a Free JSON Karate DSL Schema Generator for QA Engineers

#karate #api #backend #automation

If you work with Karate DSL for API testing, you already know how important and useful schema validation can be.

You also know how repetitive it becomes.

Writing Karate match schemas manually for every API response is one of those tasks that feels small at first until you start working with:

  • deeply nested JSON responses
  • arrays of objects
  • large payloads
  • optional fields
  • multiple endpoints

After doing this repeatedly in real automation projects, I decided to build a small utility focused on solving exactly that problem.

So I created a free browser-based tool:

JSON → Karate DSL Schema Converter

👉 https://jsonkaratedslgenerator.codeqazone.com/

The tool instantly converts a JSON payload into a ready-to-use Karate DSL schema.

The Problem

Karate DSL does not use traditional JSON Schema syntax.

Instead, it uses type matchers like:

"#string"
"#number"
"#boolean"
"#[]"
"##string"
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That approach is powerful and very readable once you understand it.

But manually transforming a real API response into a Karate validation schema can become repetitive and time-consuming.

For example, a response like this:

{
  "id": 101,
  "name": "Alice",
  "active": true,
  "roles": ["admin", "user"]
}
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Usually becomes something like:

{
  "id": "#number",
  "name": "#string",
  "active": "#boolean",
  "roles": "#[] #string"
}
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And that is a very small example.

In real-world APIs, payloads can be much larger and more nested.

What the Tool Does

The converter takes a JSON payload and automatically generates a Karate-compatible schema while preserving the original structure.

It supports:

  • primitive types
  • nested objects
  • arrays
  • arrays of objects
  • nested arrays
  • optional fields
  • copy to clipboard
  • schema download

Everything runs directly in the browser.

No installation.
No backend.
No data storage.

Just paste your JSON and generate the schema instantly.

Example Conversion

Input JSON 

{
  "id": 101,
  "name": "Alice",
  "active": true,
  "user": {
    "email": "alice@example.com",
    "profile": {
      "age": 30,
      "verified": true
    }
  },
  "orders": [
    {
      "orderId": 1,
      "amount": 99.99
    }
  ]
}
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Generated Karate Schema 

{
  "id": "#number",
  "name": "#string",
  "active": "#boolean",
  "user": {
    "email": "#string",
    "profile": {
      "age": "#number",
      "verified": "#boolean"
    }
  },
  "orders": "#[] {\"orderId\":\"#number\",\"amount\":\"#number\"}"
}
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Required vs Optional Fields

One thing I intentionally wanted in the tool was explicit control over required and optional fields in the schema.

Instead of automatically guessing business rules, the tool lets the tester define which fields are required.

Example:

id, name, user.email
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Fields included in that input remain required while all other fields are automatically converted into optional Karate matchers using the ## syntax.

That decision came directly from real QA workflows.

As testers, we usually already know:

  • which fields are mandatory
  • which fields are conditional
  • which fields depend on business logic

The tool is not trying to replace that understanding, it is simply removing the repetitive manual work.

Why I Built It

This project came from real automation work. The goal was not to create a massive platform, it was to create something:

  • fast
  • practical
  • useful immediately
  • frictionless to use

A tool you can open, use in seconds, and continue with your work.

Features

Current features include:

  • JSON → Karate DSL conversion
  • Required fields input
  • Optional field generation (##type)
  • Nested object support
  • Array schema generation
  • Demo examples
  • Copy-to-clipboard support
  • Schema download
  • Browser-only execution

Who Is This For?

This tool is especially useful for:

  • QA Automation Engineers
  • API Testers
  • Developers using Karate DSL
  • Teams building API validation suites
  • People learning Karate schema validation

Try It

👉 https://jsonkaratedslgenerator.codeqazone.com/

The app also includes:

  • Base Demo
  • Advanced Demo

so you can immediately understand how the conversion works.

If you work with Karate DSL, I hope this tool saves you some time. Feedback and suggestions are always welcome.

Happy Testing!

Top comments (1)

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gimi5555 profile image
Gilder Miller •

Thank you!
Proper schema validation in the test suite is one of the best ways to catch regression errors early, but the setup cost in Karate is often the biggest hurdle. Automating translation from JSON to DSL matchers removes a huge amount of cognitive load and a lot of potential human error during the writing process. It's a simple tool that solves a very specific, recurring pain point for QA engineers.