json-transformer

A guide for working with JSON, a common text format for storing structured data.

In plain words
What is it for?
It helps validate, format, filter, merge, flatten, query, rename, sort and convert JSON data to formats such as CSV, YAML and XML.
Why use it?
It helps inspect malformed data and reshape, compare or convert complicated JSON structures without doing each change manually.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/curiouslearner/devkit/json-transformer
Any agent
npx skills add CuriousLearner/devkit --skill json-transformer
Clone the repo
git clone --depth 1 https://github.com/CuriousLearner/devkit

Made for: Claude Code, Codex.

Per session 17 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 6,422 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.06422
Opus 5 $0.00009 $0.03211
Sonnet 5 $0.00003 $0.01284
Haiku 4.5 $0.00002 $0.00642

Measured 2d ago against content hash 39251dc61b6d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

json-transformer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/json-transformer/SKILL.md · 1,042 lines

How it starts

The opening of the file, as written. The whole thing — 1,042 lines — stays where its author put it; the contents beside it link to each section on GitHub.

JSON Transformer Skill

Transform, manipulate, and analyze JSON data structures with advanced operations.

Instructions

You are a JSON transformation expert. When invoked:

  1. Parse and Validate JSON:

    • Parse JSON from files, strings, or APIs
    • Validate JSON structure and schema
    • Handle malformed JSON gracefully
    • Pretty-print and format JSON
    • Detect and fix common JSON issues
  2. Transform Data Structures:

    • Reshape nested objects and arrays
    • Flatten and unflatten structures
    • Extract specific paths (JSONPath, JMESPath)
    • Merge and combine JSON documents
    • Filter and map data
  3. Advanced Operations:

    • Convert between JSON and other formats (CSV, YAML, XML)
    • Apply transformations (jq-style operations)
    • Query and search JSON data
    • Diff and compare JSON documents
    • Generate JSON from schemas
  4. Data Manipulation:

    • Add, update, delete properties
    • Rename keys
    • Convert data types
    • Sort and deduplicate
    • Calculate aggregate values

Usage Examples

@json-transformer data.json
@json-transformer --flatten
@json-transformer --path "users[*].email"
@json-transformer --merge file1.json file2.json
@json-transformer --to-csv data.json
@json-transformer --validate schema.json

Basic JSON Operations

Parsing and Writing

Python
import json

# Parse JSON string
data = json.loads('{"name": "John", "age": 30}')

# Parse from file
with open('data.json', 'r') as f:
    data = json.load(f)

# Write JSON to file
with open('output.json', 'w') as f:
    json.dump(data, f, indent=2)

# Pretty print
print(json.dumps(data, indent=2, sort_keys=True))

# Compact output
compact = json.dumps(data, separators=(',', ':'))

# Handle special types
from datetime import datetime
import decimal

def json_encoder(obj):
    if isinstance(obj, datetime):
        return obj.isoformat()
    if isinstance(obj, decimal.Decimal):
        return float(obj)
    raise TypeError(f"Type {type(obj)} not serializable")

json.dumps(data, default=json_encoder)

Read the full file on GitHub · 1,042 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 1,042 lines · 17 tokens per session scan A 39251dc61b6d

Subscribe to this mod's changes

json-transformer is a skill published in the GitHub repository CuriousLearner/devkit (27 stars, last pushed 10mo ago), licensed MIT. It adds 17 tokens to every session and 6,422 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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