diff --git a/artifact.data_logger/src/artifact_data_logger/core.py b/artifact.data_logger/src/artifact_data_logger/core.py
new file mode 100644
index 0000000..4171d21
--- /dev/null
+++ b/artifact.data_logger/src/artifact_data_logger/core.py
@@ -0,0 +1,87 @@
+from __future__ import annotations
+
+import json
+from dataclasses import dataclass
+from datetime import datetime
+from pathlib import Path
+from typing import Any, Dict
+from rich.console import Console
+
+
+class MetricsValidationError(Exception):
+    """Raised when the provided metrics data is invalid."""
+
+
+@dataclass
+class Metrics:
+    setup_fingerprint: str
+    policy_hash: str
+    epoch_ms: int
+    near_expiry_unpinned: float
+
+    @classmethod
+    def from_dict(cls, data: Dict[str, Any]) -> Metrics:
+        required_fields = {
+            'setup_fingerprint': str,
+            'policy_hash': str,
+            'epoch_ms': int,
+            'near_expiry_unpinned': (float, int),
+        }
+        for field_name, expected_type in required_fields.items():
+            if field_name not in data:
+                raise MetricsValidationError(f"Missing required field: {field_name}")
+            if not isinstance(data[field_name], expected_type):
+                raise MetricsValidationError(
+                    f"Invalid type for {field_name}: expected {expected_type}, got {type(data[field_name])}"
+                )
+        return cls(
+            setup_fingerprint=str(data['setup_fingerprint']),
+            policy_hash=str(data['policy_hash']),
+            epoch_ms=int(data['epoch_ms']),
+            near_expiry_unpinned=float(data['near_expiry_unpinned']),
+        )
+
+    def to_log_record(self, run_id: str) -> Dict[str, Any]:
+        ts = datetime.utcfromtimestamp(self.epoch_ms / 1000.0).isoformat() + 'Z'
+        return {
+            'run_id': run_id,
+            'timestamp': ts,
+            'setup_fingerprint': self.setup_fingerprint,
+            'policy_hash': self.policy_hash,
+            'near_expiry_unpinned': self.near_expiry_unpinned,
+        }
+
+def log_metrics(run_id: str, metrics: Dict[str, Any]) -> None:
+    """Logs experiment metrics to stdout in structured format.
+
+    Args:
+        run_id: Unique identifier of the experiment run.
+        metrics: Dictionary containing setup_fingerprint, policy_hash, epoch_ms, and near_expiry_unpinned.
+    """
+    assert isinstance(run_id, str) and run_id.strip(), "run_id must be a non-empty string"
+    assert isinstance(metrics, dict), "metrics must be a dict"
+
+    console = Console()
+    try:
+        metrics_obj = Metrics.from_dict(metrics)
+    except MetricsValidationError as err:
+        console.print(f"[bold red]Metrics validation failed:[/bold red] {err}")
+        raise
+
+    record = metrics_obj.to_log_record(run_id)
+    timestamp = record['timestamp']
+    message = (
+        f"[{timestamp}] Run {run_id}: "
+        f"setup_fingerprint={record['setup_fingerprint']} | "
+        f"policy_hash={record['policy_hash']} | "
+        f"near_expiry_unpinned={record['near_expiry_unpinned']:.4f}"
+    )
+    console.print(f"[green]Log:[/green] {message}")
+
+    # Optional: write to a local log file for CI artifact consistency
+    log_path = Path(f"metrics_log_{run_id}.txt")
+    with log_path.open('a', encoding='utf-8') as f:
+        f.write(message + '\n')
+
+    # ensure log content integrity in CI environment
+    assert log_path.exists(), "Log file should be created successfully."