Agent CLI Skill for Claude

{"event": "ready", "ts": "2026-04-30T14:00:00+00:00", "pid": 1234, "port": 8765}

"""Shared helpers for JSON CLI output."""
import json
import os
import sys
from datetime import datetime, timezone

_json_mode = False

def enable_json():
    global _json_mode
    _json_mode = True

def is_json():
    return _json_mode

def json_log(event: str, **kwargs):
    """Emit one NDJSON line to stdout."""
    obj = {"event": event, "ts": datetime.now(timezone.utc).isoformat(), **kwargs}
    print(json.dumps(obj, default=str), flush=True)

def json_error(message: str, **kwargs):
    """Emit a structured error event."""
    json_log("error", message=message, **kwargs)

def die(message: str, code: int = 1, **kwargs):
    """Print error and exit — JSON or human depending on mode."""
    if _json_mode:
        json_error(message, **kwargs)
    else:
        print(message, file=sys.stderr)
    sys.exit(code)

def add_json_flag(parser):
    """Add --json flag to an argparse parser."""
    parser.add_argument("--json", action="store_true",
                        help="NDJSON output for agent consumption")

def log(message: str, **json_kwargs):
    """Print human message normally, or emit JSON event if --json is active."""
    if _json_mode:
        json_log(json_kwargs.pop("event", "info"), message=message, **json_kwargs)
    else:
        print(message)

def json_ready(**kwargs):
    """Emit the readiness signal — only in JSON mode. Call early in daemon startup."""
    if _json_mode:
        json_log("ready", pid=os.getpid(), **kwargs)

grep -n 'print(\|sys\.exit\|exit(\|input(\|os\.system.*say' TARGET.py

from cli_utils import add_json_flag, enable_json, is_json, json_log, log, die

add_json_flag(parser)
args = parser.parse_args()
if args.json:
    enable_json()

# Before
print(f"Connected to {device}")

# After
log(f"Connected to {device}", event="connected", device=device)

# Before
print("Device not found")
sys.exit(1)

# After
die("Device not found")

# Before
print(f"Server running on port {port}")

# After — json_ready() only emits in JSON mode, so always call it + human fallback
json_ready(port=port)
log(f"Server running on port {port}", event="ready", port=port)

# Before
print(f"\r  HR {hr} RMSSD {rmssd:.1f}", end="", flush=True)

# After
if is_json():
    json_log("status", hr=hr, rmssd=rmssd)
else:
    print(f"\r  HR {hr} RMSSD {rmssd:.1f}", end="", flush=True)

if not is_json():
    print("Usage: send {\"type\": \"join\", \"name\": \"Alice\"}")

cli-utils-agent/
├── pyproject.toml
├── LICENSE                  # MIT by default, ask user
├── README.md
├── src/
│   └── cli_utils_agent/
│       ├── __init__.py      # re-exports all public API
│       └── core.py          # the implementation
├── tests/
│   ├── __init__.py
│   ├── test_json_log.py
│   ├── test_die.py
│   ├── test_log.py
│   └── test_add_json_flag.py
└── .github/
    └── workflows/
        └── test.yml         # CI with pytest

# src/cli_utils_agent/__init__.py
from .core import (
    enable_json, is_json, json_log, json_error, die,
    add_json_flag, log, json_ready,
)

__all__ = [
    "enable_json", "is_json", "json_log", "json_error", "die",
    "add_json_flag", "log", "json_ready",
]

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[project]
name = "cli-utils-agent"
version = "0.1.0"
description = "Add agent-friendly --json NDJSON output to any Python CLI"
readme = "README.md"
license = "MIT"
requires-python = ">=3.10"
classifiers = [
    "Development Status :: 4 - Beta",
    "Intended Audience :: Developers",
    "License :: OSI Approved :: MIT License",
    "Programming Language :: Python :: 3",
    "Topic :: Software Development :: Libraries",
]

[project.urls]
Homepage = "https://github.com/USER/cli-utils-agent"

[tool.hatch.build.targets.wheel]
packages = ["src/cli_utils_agent"]

# tests/test_json_log.py
import json
from cli_utils_agent import json_log, enable_json, is_json

def test_json_log_writes_ndjson(capsys):
    json_log("ready", port=8765, pid=42)
    line = capsys.readouterr().out.strip()
    obj = json.loads(line)
    assert obj["event"] == "ready"
    assert obj["port"] == 8765
    assert "ts" in obj

# tests/test_die.py
import json
import pytest
from cli_utils_agent import die, enable_json
from cli_utils_agent import core as _core

def test_die_human_mode(capsys):
    _core._json_mode = False
    with pytest.raises(SystemExit) as exc:
        die("something broke")
    assert exc.value.code == 1
    assert "something broke" in capsys.readouterr().err

def test_die_json_mode(capsys):
    _core._json_mode = True
    try:
        with pytest.raises(SystemExit):
            die("something broke", code=10)
        obj = json.loads(capsys.readouterr().out.strip())
        assert obj["event"] == "error"
        assert obj["message"] == "something broke"
    finally:
        _core._json_mode = False

# .github/workflows/test.yml
name: Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    strategy:
      matrix:
        python-version: ["3.10", "3.11", "3.12", "3.13"]
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-python@v5
        with:
          python-version: ${{ matrix.python-version }}
      - run: pip install -e ".[dev]"
      - run: pytest -v

[project.optional-dependencies]
dev = ["pytest>=8.0"]