Every agent and developer hits broken or confusing JSON. This tool handles the common headaches in one place: check whether JSON is valid with the exact error location, repair near-JSON with typos, pretty-print or minify, pull values out with a path expression, diff two documents, convert to and from YAML or CSV, produce a byte-stable canonical form for hashing, validate against a schema, and report size and structure. Same input, same output, no side effects.