diff --git a/data_analysis/src/data_analysis/cli.py b/data_analysis/src/data_analysis/cli.py
new file mode 100644
index 0000000..6f0bba5
--- /dev/null
+++ b/data_analysis/src/data_analysis/cli.py
@@ -0,0 +1,72 @@
+import argparse
+import json
+from pathlib import Path
+from typing import Any
+
+from data_analysis import core
+
+
+def _load_run_data(path: Path) -> list[dict[str, Any]]:
+    """Load and validate run data JSON file into list of dicts."""
+    if not path.exists() or not path.is_file():
+        raise FileNotFoundError(f"Input file not found: {path}")
+    with path.open('r', encoding='utf-8') as handle:
+        try:
+            data = json.load(handle)
+        except json.JSONDecodeError as e:
+            raise ValueError(f"Invalid JSON file: {path}. Error: {e}")
+
+    if not isinstance(data, list):
+        raise ValueError("Input JSON must contain a list of run data objects.")
+
+    required_fields = {"policy_hash", "warn_rate", "unknown_rate", "delta_time"}
+    for i, entry in enumerate(data):
+        if not isinstance(entry, dict):
+            raise ValueError(f"Run entry at index {i} is not a dict.")
+        missing = required_fields - set(entry)
+        if missing:
+            raise ValueError(f"Missing required fields {missing} in entry {i}.")
+
+    return data
+
+
+def _run_analysis(input_path: Path, output_path: Path) -> None:
+    """Perform analysis and write results to JSON file."""
+    data = _load_run_data(input_path)
+    warn_rate = core.calculate_warn_rate(data)
+    delta_stats = core.delta_time_distribution(data)
+
+    summary = {
+        "avg_warn_rate": warn_rate,
+        "delta_time_distribution": delta_stats,
+    }
+
+    output_path.parent.mkdir(parents=True, exist_ok=True)
+    with output_path.open('w', encoding='utf-8') as f:
+        json.dump(summary, f, indent=2, sort_keys=True)
+
+
+def main() -> None:
+    """Entry point for command-line interface."""
+    parser = argparse.ArgumentParser(
+        description="Analyze run timing data and compute summary statistics."
+    )
+    parser.add_argument(
+        "--input",
+        required=True,
+        type=Path,
+        help="Path to input JSON file containing run data.",
+    )
+    parser.add_argument(
+        "--output",
+        required=True,
+        type=Path,
+        help="Destination path for JSON file with results.",
+    )
+
+    args = parser.parse_args()
+    _run_analysis(args.input, args.output)
+
+
+if __name__ == "__main__":
+    main()