import time
import json
from functools import wraps

def traced_tool(tool_fn):
    @wraps(tool_fn)
    def wrapper(*args, **kwargs):
        start = time.time()
        result = tool_fn(*args, **kwargs)
        elapsed = time.time() - start
        print(json.dumps({
            "event": "tool_call",
            "tool": tool_fn.__name__,
            "elapsed_ms": round(elapsed * 1000),
            "result_keys": list(result.keys()) if isinstance(result, dict) else type(result).__name__
        }))
        return result
    return wrapper