jpx

JMESPath CLI and tools with 490+ functions, including 470+ extensions.

This repository contains the jpx ecosystem:

Package	Description
jpx	CLI tool with REPL, multiple output formats
jpx-mcp	MCP server for AI assistants
jpx-engine	Query engine with introspection and discovery

Quick Start

# Install
brew install joshrotenberg/brew/jpx
# or: cargo install jpx

# Use it
echo '{"name": "world"}' | jpx 'upper(name)'
# "WORLD"

curl -s https://api.github.com/users/octocat | jpx '{
  login: login,
  created: format_date(parse_date(created_at), '%B %Y')
}'
# {"login": "octocat", "created": "January 2011"}

Where jpx fits

Use jpx for shell pipelines, JSONL/NDJSON streams, agent-driven JSON work, and cases where the extraction itself should be a small, reviewable artifact. A .jpx query library can hold named, multi-line queries and be validated in CI.

Use jq when you already know it and the query is straightforward. Use a general programming language such as Python for control flow, joins across sources, retries, subprocess orchestration, or anything else that makes a query language fight the problem.

Query Libraries

Store reusable queries in a .jpx file:

-- :name active-users
-- :desc Return active user names
users[?active].name | sort(@)

-- :name summary
{
  total: length(users),
  active: length(users[?active])
}

jpx -Q queries.jpx:active-users data.json
jpx -Q queries.jpx --list-queries
jpx -Q queries.jpx --check

See Query Files for the complete format and usage guide.

Docker

# CLI
echo '{"name": "world"}' | docker run -i ghcr.io/joshrotenberg/jpx 'upper(name)'

# MCP Server
docker run -i --rm ghcr.io/joshrotenberg/jpx-mcp

MCP Server

Give Claude (or any MCP client) the ability to query and transform JSON:

{
  "mcpServers": {
    "jpx": {
      "command": "jpx-mcp"
    }
  }
}

Tools (31 total): evaluate, batch_evaluate, validate, explain, functions, describe, batch_describe, search, similar, format, diff, patch, merge, stats, paths, keys, plus an ephemeral process-scoped query store. See the MCP docs for the full list.

Function Categories

The library provides 490+ functions across these categories:

Category	Examples
String	upper, lower, split, replace, camel_case, pad_left
Array	first, last, unique, chunk, zip, flatten, group_by
Math	round, sqrt, median, stddev, percentile
Date/Time	now, parse_date, format_date, date_add, date_diff
Hash	md5, sha256, hmac_sha256, crc32
Encoding	base64_encode, base64_decode, hex_encode, url_encode
Regex	regex_match, regex_extract, regex_replace
Geo	haversine, geo_distance_km, geo_bearing
Network	cidr_contains, is_private_ip, ip_to_int
JSON Patch	json_patch, json_merge_patch, json_diff
Fuzzy	levenshtein, jaro_winkler, soundex, metaphone
Expression	map_expr, filter_expr, sort_by_expr, group_by_expr

See the documentation for the full function reference.

Acknowledgments

• JMESPath - The query language specification
• jmespath.rs - the original Rust implementation and a compatibility/benchmark reference
• jpx-core - jpx's independent JMESPath implementation with 470+ extension functions

License

MIT or Apache-2.0