JSON Formatter#

Format and validate JSON — pretty-print with configurable indentation or minify to a single line.

Input#

• A JSON string (object, array, string, number, boolean, or null)
• May be already formatted or a single minified line
• Optional action: format (default), minify, or validate-only
• Optional indent size: 2 (default) or 4 spaces

Output#

• format: Pretty-printed JSON with proper indentation and line breaks
• minify: Single-line compact JSON with no whitespace
• validate: A message confirming valid or invalid JSON (with error details)

Instructions#

1. Receive the raw JSON string from the user.

2. Determine the requested action (default: format).

3. Attempt to parse the JSON:

   • Call JSON.parse(input) conceptually — parse the string strictly following JSON spec.
   • If parsing fails, report the error with as much detail as possible (e.g., "Unexpected token at position 42", "Missing closing bracket").

4. For format action:

   • Serialize the parsed value back to a string with the requested indent size (default: 2 spaces).
   • Use JSON.stringify(parsed, null, indentSize) semantics: keys are sorted by insertion order (not alphabetically), arrays and objects are expanded across multiple lines, strings are double-quoted.

5. For minify action:

   • Serialize with no indentation or extra whitespace: JSON.stringify(parsed) semantics.

6. For validate action:

   • If parsing succeeded, report "Valid JSON" along with type and top-level key count if it is an object.
   • If parsing failed, report the error message.

7. If sort-keys option is requested, sort all object keys alphabetically at every nesting level before serializing.

8. Output the result.

Options#

• indent: 2 (default) | 4 — number of spaces per indent level
• action: format (default) | minify | validate
• sort-keys: false (default) | true — sort object keys alphabetically

Examples#

Format (default, 2-space indent)

Input:

text

{"name":"Alice","age":30,"hobbies":["reading","coding"]}

Output:

json

{
  "name": "Alice",
  "age": 30,
  "hobbies": [
    "reading",
    "coding"
  ]
}

Minify

Input:

json

{
  "name": "Alice",
  "age": 30
}

Output:

text

{"name":"Alice","age":30}

Validate — invalid JSON

Input:

text

{name: 'Alice', age: 30}

Output:

text

Invalid JSON: Unexpected token 'n' at position 1. Keys must be double-quoted strings and string values must use double quotes, not single quotes.

Format with 4-space indent and sort-keys

Input:

text

{"z":3,"a":1,"m":2}

Output:

json

{
    "a": 1,
    "m": 2,
    "z": 3
}

Error Handling#

• If the input is empty or whitespace-only, respond: "No input provided. Please paste a JSON string."
• If JSON.parse fails, report the error message and the approximate position or line number if determinable. Do not attempt to silently fix the JSON — report the exact parse error. (If the user wants repair, suggest using the json-repair skill.)
• If the input is valid JSON but the user asked to "format" a primitive (e.g., just 42 or "hello"), format it as-is (a primitive is valid JSON).
• Never truncate the output — always return the full formatted result.