json-to-schema

Generate JSON Schema (draft-07) from sample JSON data. It handles nested objects, arrays, type detection, and can merge multiple samples into one schema.

Install

npm install -g @lxgicstudios/json-to-schema

Or run directly:

npx @lxgicstudios/json-to-schema data.json

Features

• Draft-07 output - Generates valid JSON Schema draft-07
• Type inference - Detects string, number, integer, boolean, null, object, array
• Format detection - Recognizes date-time, email, URI, UUID, IPv4, IPv6
• Schema merging - Combine multiple samples into one schema
• Required fields - Mark all fields as required with one flag
• Nested support - Handles deeply nested objects and arrays
• JSONL support - Process multiple JSON objects per file
• Pipe-friendly - Works great with stdin/stdout
• Colorized output - Pretty terminal output with syntax highlighting
• Zero dependencies - Built with Node.js builtins only

Usage

# From a file
json-to-schema data.json

# From stdin
echo '{"name":"John","age":30,"email":"[email protected]"}' | json-to-schema

# Merge multiple samples
json-to-schema --merge -f sample1.json -f sample2.json

# All fields required
json-to-schema --required data.json

# With title and description
json-to-schema --title "User" --description "A user object" data.json

# Pipe from an API
curl -s https://api.example.com/users/1 | json-to-schema --title "User"

# Compact output
json-to-schema --compact data.json

Options

| Option | Description | Default | |--------|-------------|---------| | -f, --file <path> | Input JSON file (repeatable) | - | | --merge | Merge schemas from multiple samples | false | | --required | Mark all fields as required | false | | --title <title> | Schema title | - | | --description <desc> | Schema description | - | | --additional | Allow additional properties | false | | --no-format | Skip format detection | false | | --compact | No indentation in output | false | | --help | Show help | - |

Example Output

Input:

{
  "id": 1,
  "name": "John Doe",
  "email": "[email protected]",
  "active": true,
  "tags": ["admin", "user"]
}

Output:

{
  "$schema": "http://json-schema.org/draft-07/schema#",
  "type": "object",
  "properties": {
    "id": { "type": "integer" },
    "name": { "type": "string" },
    "email": { "type": "string", "format": "email" },
    "active": { "type": "boolean" },
    "tags": {
      "type": "array",
      "items": { "type": "string" }
    }
  },
  "additionalProperties": false
}

Built by LXGIC Studios

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