diff --git a/tools/op_source_inventory.py b/tools/op_source_inventory.py
new file mode 100644
index 0000000..bff793f
--- /dev/null
+++ b/tools/op_source_inventory.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python3
+"""Build a JSON inventory of mcoplib operator source groups."""
+
+from __future__ import annotations
+
+import argparse
+import json
+from pathlib import Path
+
+GROUPS = {
+    "vllm": "op/vllm",
+    "sglang": "op/sglang",
+    "lmdeploy": "op/lmdeploy",
+    "cv": "op/cv",
+    "native": "op",
+}
+
+SOURCE_SUFFIXES = {".cu", ".cuh", ".cpp", ".cc", ".h", ".hpp", ".py"}
+
+
+def _sources(root: Path, relative_dir: str) -> list[str]:
+    base = root / relative_dir
+    if not base.exists():
+        return []
+    return sorted(
+        path.relative_to(root).as_posix()
+        for path in base.rglob("*")
+        if path.is_file() and path.suffix in SOURCE_SUFFIXES
+    )
+
+
+def build_inventory(root: Path) -> dict[str, object]:
+    raw_files: dict[str, list[str]] = {}
+    for name, relative_dir in GROUPS.items():
+        raw_files[name] = _sources(root, relative_dir)
+
+    other_files: set[str] = set()
+    for name in GROUPS:
+        if name != "native":
+            other_files.update(raw_files[name])
+    if "native" in raw_files:
+        raw_files["native"] = [path for path in raw_files["native"] if path not in other_files]
+
+    groups: dict[str, object] = {}
+    for name, relative_dir in GROUPS.items():
+        files = raw_files[name]
+        groups[name] = {"root": relative_dir, "count": len(files), "files": files}
+    return {"root": str(root), "groups": groups}
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description="Create mcoplib operator source inventory.")
+    parser.add_argument("--root", type=Path, default=Path(__file__).resolve().parents[1])
+    parser.add_argument("--output", type=Path)
+    args = parser.parse_args()
+
+    payload = build_inventory(args.root.resolve())
+    text = json.dumps(payload, indent=2, sort_keys=True)
+    if args.output:
+        args.output.parent.mkdir(parents=True, exist_ok=True)
+        args.output.write_text(text + "\n", encoding="utf-8")
+    else:
+        print(text)
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())
diff --git a/unit_test/test_op_source_inventory.py b/unit_test/test_op_source_inventory.py
new file mode 100644
index 0000000..58a1bae
--- /dev/null
+++ b/unit_test/test_op_source_inventory.py
@@ -0,0 +1,30 @@
+import tempfile
+import unittest
+from pathlib import Path
+
+import sys
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
+
+from tools.op_source_inventory import build_inventory
+
+
+class OpSourceInventoryTest(unittest.TestCase):
+    def test_inventory_counts_group_sources(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            (root / "op" / "vllm").mkdir(parents=True)
+            (root / "op" / "vllm" / "kernel.cu").write_text("", encoding="utf-8")
+            (root / "op" / "vllm" / "README.md").write_text("", encoding="utf-8")
+            (root / "op" / "native_kernel.cu").write_text("", encoding="utf-8")
+
+            inventory = build_inventory(root)
+
+        self.assertEqual(inventory["groups"]["vllm"]["count"], 1)
+        self.assertEqual(inventory["groups"]["vllm"]["files"], ["op/vllm/kernel.cu"])
+        self.assertEqual(inventory["groups"]["native"]["count"], 1)
+        self.assertEqual(inventory["groups"]["native"]["files"], ["op/native_kernel.cu"])
+
+
+if __name__ == "__main__":
+    unittest.main()