Json Modifier

Safely apply structured JSON patches (RFC 6902) to files. Use this skill when you need to update configuration files, package.json, or memory JSONs without rewriting the whole file or using brittle regex.

A utility for modifying JSON files using RFC 6902 JSON Patch format. Supports precise additions, removals, replacements, moves, copies, and tests.

Usage

# Modify a file in place
node skills/json-modifier/index.js --file path/to/config.json --patch '[{"op": "replace", "path": "/key", "value": "new_value"}]'

# Modify and save to a new file
node skills/json-modifier/index.js --file input.json --patch '[...]' --out output.json

# Use a patch file
node skills/json-modifier/index.js --file input.json --patch-file patches/update.json

Patch Format (RFC 6902)

The patch must be a JSON array of operation objects.

Examples

Replace a value:

[
  { "op": "replace", "path": "/version", "value": "2.0.0" }
]

Add a new key:

[
  { "op": "add", "path": "/features/new_feature", "value": true }
]

Remove a key:

[
  { "op": "remove", "path": "/deprecated_key" }
]

Append to an array:

[
  { "op": "add", "path": "/list/-", "value": "item" }
]

Safety

• Validates patch against document before applying.
• Atomic write (writes to temporary file, then renames).
• Preserves indentation (default: 2 spaces).