Add lookup_barcode tool

README.md

@@ -127,6 +127,7 @@ cached session, so it also overrides a stale cached timezone.
 |------|-------------|
 | `search_foods` | Search the Cronometer food database by name |
 | `get_food_details` | Full nutrition profile and serving sizes for a food |
+| `lookup_barcode` | Find foods by the barcode on their package (EAN, UPC or GTIN), like the app's scanner |
 
 ### Diary Management
 

src/cronometer_api_mcp/client.py

@@ -642,6 +642,30 @@ def get_foods(self, food_ids: list[int]) -> list[dict]:
         logger.info("Batch-fetched %d/%d foods", len(foods), len(food_ids))
         return foods
 
+    def lookup_barcode(self, barcode: str) -> list[dict]:
+        """Find foods by product barcode, as the app's scanner does.
+
+        Uses /api/v2/barcode, which answers with full food objects (the same
+        shape as get_food). The server matches loosely: leading zeros are
+        ignored (UPC-A "049000050103" finds foods stored as "49000050103")
+        and a placeholder code like "0000000000000" returns unrelated foods
+        whose stored barcode is "0". So the code is validated first (all zeros
+        is refused) and only foods that actually carry it are returned. An unknown code returns
+        an empty list.
+        """
+        (code,) = normalize_barcodes([barcode])
+        if not code.strip("0"):
+            raise ValueError(f"barcode {barcode!r} is all zeros, not a product code")
+        payload = {"query": code, "config": {"call_version": 2}}
+        data = self._request("/api/v2/barcode", payload)
+        foods = [
+            f
+            for f in data.get("foods") or []
+            if any(b.lstrip("0") == code.lstrip("0") for b in f.get("barcodes") or [])
+        ]
+        logger.info("Barcode %s matched %d foods", code, len(foods))
+        return foods
+
     # ------------------------------------------------------------------
     # Custom food creation
     # ------------------------------------------------------------------

src/cronometer_api_mcp/server.py

@@ -571,6 +571,46 @@ def get_food_details(food_id: int) -> str:
         return _err(e)
 
 
+@mcp.tool(annotations=_READ_ONLY)
+def lookup_barcode(barcode: str) -> str:
+    """Find foods by the barcode on their package (EAN, UPC or GTIN).
+
+    The same lookup the app's barcode scanner does. Returns each matching
+    food with the measure_ids needed for add_food_entry; an empty list means
+    Cronometer doesn't know the code (search_foods by name instead).
+
+    Args:
+        barcode: The digits under the bars, e.g. "4006381333931". Spaces and
+            dashes are fine; the check digit is verified.
+    """
+    try:
+        client = _get_client()
+        foods = client.lookup_barcode(barcode)
+        results = []
+        for f in foods:
+            results.append(
+                {
+                    "food_id": f.get("id"),
+                    "name": f.get("name"),
+                    "source": f.get("source"),
+                    "default_measure_id": f.get("defaultMeasureId"),
+                    "measures": [
+                        {
+                            "measure_id": m.get("id"),
+                            "name": m.get("name"),
+                            "grams": m.get("value"),
+                            "quantity": m.get("amount"),
+                        }
+                        for m in f.get("measures", [])
+                    ],
+                    "barcodes": f.get("barcodes", []),
+                }
+            )
+        return _ok({"barcode": barcode, "count": len(results), "foods": results})
+    except Exception as e:
+        return _err(e)
+
+
 # ------------------------------------------------------------------
 # Custom food creation
 # ------------------------------------------------------------------

tests/test_barcode.py

@@ -1,4 +1,4 @@
-"""Tests for barcode validation of custom foods.
+"""Tests for barcode validation and lookup.
 
 normalize_barcodes accepts the GTIN family (EAN-13, UPC-A, EAN-8, UPC-E,
 GTIN-14), strips the spaces and dashes codes are printed with, and verifies
@@ -8,6 +8,7 @@
 from __future__ import annotations
 
 import pytest
+from test_client import make_cold_client
 
 from cronometer_api_mcp.barcode import normalize_barcodes
 
@@ -66,3 +67,62 @@ def test_normalize_barcodes_drops_duplicates():
     assert normalize_barcodes(["4006381333931", "4006 3813 3393 1"]) == [
         "4006381333931"
     ]
+
+
+# ---------------------------------------------------------------------------
+# lookup_barcode
+# ---------------------------------------------------------------------------
+
+
+def _food(food_id: int, barcodes: list[str]) -> dict:
+    return {"id": food_id, "name": f"Food {food_id}", "barcodes": barcodes}
+
+
+def test_lookup_barcode_sends_normalized_code(tmp_path):
+    hit = _food(1, ["4006381333931"])
+    client, state = make_cold_client(tmp_path, [{"foodId": 1, "foods": [hit]}])
+
+    assert client.lookup_barcode("400 6381 33393 1") == [hit]
+    assert state["payloads"][0]["query"] == "4006381333931"
+    assert state["payloads"][0]["config"] == {"call_version": 2}
+
+
+def test_lookup_barcode_matches_codes_stored_without_leading_zeros(tmp_path):
+    stored = _food(1, ["10694026", "49000050103"])
+    client, _ = make_cold_client(tmp_path, [{"foodId": 1, "foods": [stored]}])
+
+    assert client.lookup_barcode("049000050103") == [stored]
+
+
+def test_lookup_barcode_drops_foods_without_the_code(tmp_path):
+    """The server answers a placeholder-like code with unrelated foods whose
+    stored barcode is "0"; those must not come back as matches."""
+    hit = _food(1, ["4006381333931"])
+    junk = _food(2, ["0"])
+    client, _ = make_cold_client(tmp_path, [{"foodId": 2, "foods": [junk, hit]}])
+
+    assert client.lookup_barcode("4006381333931") == [hit]
+
+
+def test_lookup_barcode_unknown_code_returns_empty(tmp_path):
+    client, _ = make_cold_client(tmp_path, [{"result": "SUCCESS", "messages": []}])
+
+    assert client.lookup_barcode("4006381333931") == []
+
+
+def test_lookup_barcode_rejects_bad_check_digit_before_request(tmp_path):
+    client, state = make_cold_client(tmp_path, [{"foods": []}])
+
+    with pytest.raises(ValueError, match="check digit"):
+        client.lookup_barcode("4006381333932")
+    assert state["payloads"] == []
+
+
+def test_lookup_barcode_rejects_all_zeros(tmp_path):
+    """All zeros passes the check digit but would match every food stored
+    with the placeholder barcode "0"."""
+    client, state = make_cold_client(tmp_path, [{"foods": []}])
+
+    with pytest.raises(ValueError, match="all zeros"):
+        client.lookup_barcode("0000000000000")
+    assert state["payloads"] == []

tests/test_server_import.py

@@ -27,6 +27,7 @@
     "get_nutrition_scores",
     "import_recipe",
     "list_biometrics",
+    "lookup_barcode",
     "mark_day_complete",
     "remove_food_entry",
     "search_foods",