diff --git a/spectrometer.py b/spectrometer.py
new file mode 100644
index 0000000..9a03b35
--- /dev/null
+++ b/spectrometer.py
@@ -0,0 +1,44 @@
+"""Thin wrapper for external tools — outputs JSON to stdout."""
+
+import argparse
+import json
+import sys
+
+from hpcs6500 import HPCS6500, find_hpcs_port
+
+
+def measure():
+    port = find_hpcs_port()
+    if not port:
+        print('{"error": "HPCS 6500 not found"}', file=sys.stderr)
+        sys.exit(1)
+
+    dev = HPCS6500(port)
+    try:
+        dev.identify()
+        dev.psu_on()
+        reading = dev.take_reading(psu=False)
+    finally:
+        dev.psu_off()
+        dev.close()
+
+    if reading is None:
+        print('{"error": "measurement failed"}', file=sys.stderr)
+        sys.exit(1)
+
+    result = {
+        "lumen": round(reading["Phi_lm"], 1),
+        "cct": round(reading["CCT_K"]),
+    }
+    print(json.dumps(result))
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="HPCS 6500 JSON interface")
+    parser.add_argument("--measure", action="store_true", help="Take a measurement and output JSON")
+    args = parser.parse_args()
+
+    if args.measure:
+        measure()
+    else:
+        parser.print_help()