diff --git a/tests/test_summarize_counters.py b/tests/test_summarize_counters.py
new file mode 100644
index 0000000..21a89f3
--- /dev/null
+++ b/tests/test_summarize_counters.py
@@ -0,0 +1,29 @@
+import csv
+import tempfile
+import unittest
+from pathlib import Path
+
+from tools.summarize_counters import summarize
+
+
+class SummarizeCountersTest(unittest.TestCase):
+    def test_counts_metric_types_and_duplicates(self):
+        with tempfile.TemporaryDirectory() as tmpdir:
+            path = Path(tmpdir) / "counters.csv"
+            with path.open("w", newline="", encoding="utf-8") as handle:
+                writer = csv.writer(handle)
+                writer.writerow(["1", "Gauge", "mx_gpu_temp"])
+                writer.writerow(["2", "Gauge", "mx_gpu_temp"])
+                writer.writerow(["3", "Counter", "mx_error_count"])
+                writer.writerow(["4", "Gauge", ""])
+                writer.writerow(["5", "", "mx_ignored"])
+
+            summary = summarize(path)
+
+        self.assertEqual(summary["metric_count"], 3)
+        self.assertEqual(summary["type_counts"], {"Counter": 1, "Gauge": 2})
+        self.assertEqual(summary["duplicate_metric_names"], ["mx_gpu_temp"])
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/tools/summarize_counters.py b/tools/summarize_counters.py
new file mode 100644
index 0000000..ed61586
--- /dev/null
+++ b/tools/summarize_counters.py
@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+"""Summarize mx-exporter counter CSV files as JSON."""
+
+from __future__ import annotations
+
+import argparse
+import csv
+import json
+from collections import Counter
+from pathlib import Path
+
+
+def summarize(path: Path) -> dict[str, object]:
+    type_counts: Counter[str] = Counter()
+    metric_names: list[str] = []
+    with path.open(newline="", encoding="utf-8") as handle:
+        for row in csv.reader(handle):
+            if not row or not "".join(row).strip() or row[0].lstrip().startswith("#"):
+                continue
+            if len(row) < 3:
+                continue
+            metric_type = row[1].strip()
+            metric_name = row[2].strip()
+            if metric_type and metric_name:
+                type_counts[metric_type] += 1
+                metric_names.append(metric_name)
+    duplicates = sorted(name for name, count in Counter(metric_names).items() if count > 1)
+    return {
+        "path": str(path),
+        "metric_count": len(metric_names),
+        "type_counts": dict(sorted(type_counts.items())),
+        "duplicate_metric_names": duplicates,
+    }
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "path",
+        nargs="?",
+        type=Path,
+        default=Path(__file__).resolve().parents[1] / "mx_exporter" / "default-counters.csv",
+    )
+    parser.add_argument("--output", type=Path, help="write summary JSON to this path")
+    args = parser.parse_args()
+
+    if not args.path.is_file():
+        parser.error(f"input file does not exist: {args.path}")
+
+    payload = summarize(args.path)
+    text = json.dumps(payload, indent=2, ensure_ascii=False)
+    if args.output:
+        args.output.write_text(text + "\n", encoding="utf-8")
+    else:
+        print(text)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())