@master4n/master-cli (mfn)

Master CLI for developers and AI agents. 51 headless, JSON-first commands in three families: token savers (extract exactly what you need — one JSON field, a line range, a file outline — instead of dumping whole files into context), exact computation (BigInt math, semver, cron, regex, timezones — verified answers instead of guesses), and one-call actions (free a port, wait for a server, bulk-replace with dry-run). Every command runs the same for a human at a terminal and for an agent reading stdout, in ~60ms.

Installation

npm install -g @master4n/master-cli

This installs the mfn command.

Zero-install (agents & one-off use)

No global install needed — npx runs any command directly:

npx -y @master4n/master-cli capabilities --json   # discover every command
npx -y @master4n/master-cli epoch 1622547800 --json

For AI agents: run mfn capabilities --json (or the npx form above) to get the machine-readable manifest, and read llms.txt — it ships inside the npm package and documents the full agent contract.

The contract (why it's agent-friendly)

• Headless-first — every command runs from flags/stdin. Interactive prompts appear only on a TTY when required input is missing; with --json or when piped, commands never block.
• Machine-readable — pass --json (or just pipe; non-TTY auto-emits) and you get exactly one JSON object on stdout: { "ok": true, ... } on success, { "ok": false, "error", "message" } on failure.
• Stable exit codes — 0 success · 1 runtime error · 2 usage error.
• Clean channels — the banner, spinners, and logs go to stderr; stdout carries only data, so mfn <cmd> --json | jq always works.
• Strict parsing — unknown commands/flags and missing args fail loudly ({ok:false}, exit 2), never a silent "success".
• Self-describing — mfn capabilities --json lists every command, and llms.txt documents the full agent contract.

MCP server (built in)

For agent clients that can't run shell commands, mfn mcp serves the whole toolkit over the Model Context Protocol (stdio transport, zero extra dependencies):

// e.g. .mcp.json / claude_desktop_config.json / any MCP client
{
  "mcpServers": {
    "mfn": { "command": "npx", "args": ["-y", "@master4n/master-cli@latest", "mcp"] }
  }
}

Three tools: mfn_capabilities (the manifest), mfn_run ({command, args[]} — runs any catalogued command and returns its single JSON object, guardrails included), and mfn_help (per-command flags). update is deny-listed so an MCP-only client can never install packages. mfn mcp --json describes the server without starting it.

An Agent Skill ships at skills/mfn/SKILL.md — a portable SKILL.md (YAML frontmatter + usage guide) that teaches any coding agent (Claude Code, Roo, Cline, …) the full command catalog, output contract, recipes, and gotchas. .claude/skills/mfn symlinks to it so Claude Code auto-discovers it in this repo; point other agents at the file directly.

This repo ships a .mcp.json with exactly this wiring, so cloning it gives Claude Code (and any client honouring project-scope MCP config) the mfn server automatically.

Quick start

mfn -h                 # top-level help (lists every command)
mfn <command> -h       # per-command help: flags + examples
mfn -v                 # version
mfn capabilities --json   # machine-readable manifest of all commands

Commands (51)

Run mfn capabilities for the grouped list, mfn <command> --help for flags.

OS-level — one call on macOS, Windows, and Linux

Command	What it does	Example
clip	Read/write the system clipboard	git diff | mfn clip --json
notify	Desktop notification — ping the user when a task finishes	mfn notify "build finished" --json
open	Open a file/URL in the default app (validated first)	mfn open coverage/index.html --json
procs	Search processes by name: pid/cpu/mem	mfn procs node --json
disk	Per-mount disk usage without df parsing	mfn disk --json
trash	Reversible delete to the OS trash — never rm -rf	mfn trash old-logs --json
dns	A/AAAA/CNAME/MX/TXT/NS in one call	mfn dns github.com --json

Token savers — read less, extract exactly

Command	What it does	Example
json	One value from JSON by path — don't read the document	mfn json scripts.build -f package.json --json
schema	Infer JSON shape (paths + types); 10MB payload → ~20 lines	mfn schema -f response.json --json
count	Lines/words/chars/bytes + LLM token estimate	git diff | mfn count --json
lines	Exact line range of a file (1-based), never the whole file	mfn lines src/app.ts -s 120 -n 30 --json
outline	Symbols + line numbers (.ts .js .py .go .md)	mfn outline src/app.ts --json
diff	Structured hunks of two files, counts first	mfn diff old.json new.json -s --json
freq	Most repeated lines — log triage in one call	mfn freq error.log -t 5 --json
imports	A file's imports, or who imports a module	mfn imports --who utility --json
repo	Git branch/dirty/ahead-behind/commits in one object	mfn repo --json
sys / have / ip	System facts · tool versions · local addresses	mfn have node git docker --json
size / ext / recent	Disk usage · composition by extension · newest files	mfn size -t 5 --json
ports	ALL listening TCP ports with owning processes	mfn ports --json
pkg	Declared vs installed dependency versions	mfn pkg --json
env / dotenv	Env inspection (secrets always redacted) · .env completeness	mfn dotenv --json

Exact computation — never guess

Command	What it does	Example
calc	BigInt-exact arithmetic — 2^53 + 1 comes out right	mfn calc "2^53 + 1" --json
base	hex/dec/bin/oct conversion, BigInt-safe	mfn base 0xff --json
semver	Validate/compare/sort/bump per semver.org	mfn semver 1.10.0 1.9.2 --json
cron	Validate + explain + next run times	mfn cron "*/15 9-17 * * 1-5" --json
regex	Test a pattern — matches with line/index/groups	mfn regex "TODO" -f src/app.ts --json
url	URL → components + decoded query params	mfn url "https://x.com/a?b=1" --json
escape	Context-exact escaping: shell, JSON, regex, HTML, URL	mfn escape "it's" --json
case	camel/snake/kebab/pascal/… conversion	mfn case getUserName -t snake --json
epoch / date	Epoch ↔ date (auto unit) · timezone conversion	mfn epoch 1622547800 --json
decode	JWT header + payload + expiry (signature not verified)	mfn decode -t <jwt> --json

Actions — do, don't script

Command	What it does	Example
replace	Literal find/replace across files — dry-run by default	mfn replace old new -g "src/**/*.ts" --json
wait	Block until port/URL/file is ready — no sleep loops	mfn wait -p 3000 -t 30 --json
kill	Free the ports your dev server got stuck on	mfn kill -p 3000 8080 -y --json
http	Probe a URL: status/headers/timing, capped body preview	mfn http localhost:3000/health --json
port	Find a free port, or check one	mfn port -c 3000 --json
id / hash / encode / random	UUID v4/v7/nano · digests · codecs · CSPRNG	mfn id -t uuid7 -n 3 --json
sc / cts	Fuzzy file find · directory tree	mfn sc service --json
capabilities / update	Machine-readable manifest · self-update	mfn capabilities --json
mcp	Serve every command over the Model Context Protocol (stdio)	mfn mcp

Examples

# Timestamps: any unit in, readable date out (parse cleanly in a script)
mfn epoch 1622547800000 --json | jq -r '.utc'        # 2021-06-01 11:43:20.000

# Free the ports your dev server got stuck on
mfn kill -p 3000 5173 -y --json

# Inspect a JWT without a website
mfn decode -t "$TOKEN" --json | jq '.payload.exp'

# Hand an agent the repo layout
mfn cts --json | jq -r '.tree'

Notes

• Date/time features are powered by @master4n/temporal-transformer v2 (Luxon-backed, integer epochs, yyyy-MM-dd HH:mm:ss tokens).
• Process/port/package operations use execFile (no shell), so inputs cannot inject commands.

Part of the @master4n toolkit

A small ecosystem of focused, agent-friendly packages:

• @master4n/temporal-transformer — epoch/timestamp ↔ date conversion with auto unit-detection and IANA timezones (Luxon-backed)
• @master4n/temporal-transformer-codemod — codemod to migrate temporal-transformer v1→v2
• @master4n/http-status — machine-readable HTTP status-code registry for apps & AI agents
• @master4n/decorators — zero-dependency TypeScript decorators (DI, validation, resilience, redaction)

License

MIT © Master4Novice