Add add_biometric tool to record weight, body fat and other readings

README.md

@@ -151,6 +151,7 @@ cached session, so it also overrides a stale cached timezone.
 | `get_fasting_stats` | Aggregate fasting statistics |
 | `list_biometrics` | List trackable biometric metrics and their units |
 | `get_biometrics` | Biometric time series (e.g. weight, body fat) within a date range |
+| `add_biometric` | Record a biometric reading such as a weight or body fat |
 
 All date parameters use `YYYY-MM-DD` format and default to today when omitted.
 

src/cronometer_api_mcp/client.py

@@ -1960,6 +1960,65 @@ def get_biometrics(
         )
         return data
 
+    def add_biometric(
+        self,
+        metric_id: int,
+        unit_id: int,
+        amount: float,
+        day: date | None = None,
+    ) -> dict:
+        """Record a biometric value (e.g. a weight or body fat reading).
+
+        Args:
+            metric_id: Metric ID from get_metrics (e.g. 1 for Weight,
+                8 for Body Fat).
+            unit_id: Unit ID from that metric's units (e.g. 1 for kg, 2 for
+                lbs). The value is stored in this unit.
+            amount: The reading.
+            day: Date of the reading. Defaults to today.
+
+        Several readings of one metric can share a day; get_biometrics then
+        reports their average. A reading on an earlier day doesn't change
+        the profile's current weight.
+
+        Uses: POST /api/v2/add_biometric
+
+        Returns {"biometricId": int, "metricId", "unitId", "amount", "day"}.
+        """
+        if not math.isfinite(amount) or amount < 0:
+            raise ValueError(f"amount must be a non-negative number, got {amount}")
+        biometric = {
+            "biometricId": 0,
+            "type": "Biometric",
+            "metricId": metric_id,
+            "unitId": unit_id,
+            "amount": amount,
+            "day": self._format_day(day),
+            "order": 1,
+            "meta": None,
+            "externalId": None,
+            "source": None,
+            "userId": self.user_id,
+        }
+        payload = {"biometric": biometric, "config": {"call_version": 1}}
+        data = self._request("/api/v2/add_biometric", payload)
+        if not data.get("id"):
+            raise CronometerError(f"Failed to add biometric: {data}")
+        logger.info(
+            "Recorded metric %d = %s (unit %d) on %s",
+            metric_id,
+            amount,
+            unit_id,
+            biometric["day"],
+        )
+        return {
+            "biometricId": data["id"],
+            "metricId": metric_id,
+            "unitId": unit_id,
+            "amount": amount,
+            "day": (day or self.today()).isoformat(),
+        }
+
 
 # ======================================================================
 # Helpers

src/cronometer_api_mcp/server.py

@@ -1043,6 +1043,35 @@ def get_biometrics(
         return _err(e)
 
 
+@mcp.tool(annotations=_WRITE)
+def add_biometric(
+    metric_id: int,
+    unit_id: int,
+    amount: float,
+    date: str | None = None,
+) -> str:
+    """Record a biometric reading such as a weight or body fat.
+
+    Use list_biometrics for metric_id and unit_id (e.g. Weight is metric_id 1
+    with unit_id 1 for kg; Body Fat is metric_id 8 with unit_id 13 for %).
+    The reading appears in get_food_log's diary as a "Biometric" entry;
+    remove_food_entry with its biometricId deletes it.
+
+    Args:
+        metric_id: Numeric metric ID from list_biometrics.
+        unit_id: Numeric unit ID from the metric's units; the amount is in
+            this unit.
+        amount: The reading.
+        date: Date as YYYY-MM-DD (defaults to today).
+    """
+    try:
+        client = _get_client()
+        result = client.add_biometric(metric_id, unit_id, amount, _parse_date(date))
+        return _ok({"biometric": result})
+    except Exception as e:
+        return _err(e)
+
+
 # ------------------------------------------------------------------
 # Helpers
 # ------------------------------------------------------------------

tests/test_biometrics_write.py

@@ -0,0 +1,53 @@
+"""add_biometric: record a reading through /api/v2/add_biometric."""
+
+from __future__ import annotations
+
+import math
+from datetime import date
+
+import pytest
+from test_client import make_cold_client
+
+from cronometer_api_mcp.client import CronometerError
+
+ADDED = {"heightInCM": 180, "weightInKG": 80.0, "messages": [], "id": 1894305060}
+
+
+def test_add_biometric_sends_new_reading(tmp_path):
+    client, state = make_cold_client(tmp_path, [ADDED])
+
+    result = client.add_biometric(1, 2, 165.5, date(1900, 1, 2))
+
+    sent = state["payloads"][0]
+    assert sent["config"] == {"call_version": 1}
+    assert sent["biometric"] == {
+        "biometricId": 0,
+        "type": "Biometric",
+        "metricId": 1,
+        "unitId": 2,
+        "amount": 165.5,
+        "day": "1900-1-2",
+        "order": 1,
+        "meta": None,
+        "externalId": None,
+        "source": None,
+        "userId": 42,
+    }
+    assert result["biometricId"] == 1894305060
+    assert result["day"] == "1900-01-02"
+
+
+@pytest.mark.parametrize("bad", [-1.0, math.nan, math.inf])
+def test_add_biometric_rejects_bad_amounts(tmp_path, bad):
+    client, state = make_cold_client(tmp_path, [ADDED])
+
+    with pytest.raises(ValueError, match="non-negative"):
+        client.add_biometric(1, 1, bad)
+    assert state["payloads"] == []
+
+
+def test_add_biometric_raises_without_id(tmp_path):
+    client, _ = make_cold_client(tmp_path, [{"messages": []}])
+
+    with pytest.raises(CronometerError, match="Failed to add biometric"):
+        client.add_biometric(1, 1, 70.0)

tests/test_server_import.py

@@ -12,6 +12,7 @@
 import threading
 
 EXPECTED_TOOLS = {
+    "add_biometric",
     "add_custom_food",
     "add_food_entry",
     "add_recipe",