I built a tool to generate OpenAPI (Swagger) specifications from JSON in seconds

Introduction

In API development, writing OpenAPI (Swagger) specifications is an unavoidable task, but honestly, it's tedious, isn't it?

Especially when you already have an implemented API or an external API response example (JSON), there are many times when you think, "I want to convert this JSON structure directly into a YAML schema definition."
Handwriting type: object or nesting properties takes time and is prone to indentation errors.

Therefore, I created a tool that converts JSON into an OpenAPI Schema object (YAML) instantly just by pasting it.

https://devtoolkits.app/ja/tools/json-to-openapi

What kind of tool?

"JSON to OpenAPI Converter" is a developer tool that runs in the browser.
When you paste JSON into the area on the left, an OpenAPI 3.0 / 3.1 compliant YAML schema is generated in real-time on the right.

Features

• ⚡ Real-time conversion: It converts as you type, so there's no waiting time.
• 📝 Accurate type inference: It automatically identifies strings (string), numbers (number/integer), booleans (boolean), arrays (array), and objects (object).
• 🌳 Supports deep nesting: It recursively analyzes complex JSON structures and outputs them with correct indentation.
• 📋 One-click copy: The generated YAML can be copied to the clipboard with a single button.

How to use

The usage is very simple.

1. Access JSON to OpenAPI Converter.
2. Paste the JSON you want to convert into the text area on the left.
3. The generated YAML will be displayed on the right, so copy and paste it into your OpenAPI definition file (such as openapi.yaml).

Conversion Example

For example, if you input JSON like the following:

{
  "id": 123,
  "name": "User Name",
  "tags": ["admin", "editor"],
  "profile": {
    "active": true
  }
}

The following YAML will be generated:

type: object
properties:
  id:
    type: integer
  name:
    type: string
  tags:
    type: array
    items:
      type: string
  profile:
    type: object
    properties:
      active:
        type: boolean

Conclusion

Creating API specifications should be focused on "essential design" rather than being consumed by the task of "writing YAML."
I would be happy if this tool helps improve the efficiency of your daily development work, even just a little.

DevToolkits also offers other tools to make an engineer's "small tasks" easier. Please check them out.