diff --git a/src/tools.rs b/src/tools.rs
index a5392e0..4c88dd1 100644
--- a/src/tools.rs
+++ b/src/tools.rs
@@ -503,7 +503,32 @@ impl NutritionServer {
 
         // Build nutriments JSON — include calories in the energy-kcal_100g field
         let mut nutriments = params.nutriments.unwrap_or(json!({}));
+
+        // Translate friendly key names (as documented in the schema) to the
+        // OFF-style _100g keys that sum_nutriments() looks for. Callers may
+        // also pass OFF keys directly — those pass through unchanged.
+        let friendly_to_off: &[(&str, &str)] = &[
+            ("protein", "proteins_100g"),
+            ("carbohydrates", "carbohydrates_100g"),
+            ("fat", "fat_100g"),
+            ("fiber", "fiber_100g"),
+            ("sugars", "sugars_100g"),
+            ("saturated_fat", "saturated-fat_100g"),
+            ("salt", "salt_100g"),
+            ("fructose", "fructose_100g"),
+            ("alcohol", "alcohol_100g"),
+            ("potassium", "potassium_100g"),
+            ("calcium", "calcium_100g"),
+            ("magnesium", "magnesium_100g"),
+            ("cholesterol", "cholesterol_100g"),
+        ];
+
         if let Some(obj) = nutriments.as_object_mut() {
+            for (friendly, off_key) in friendly_to_off {
+                if let Some(val) = obj.remove(*friendly) {
+                    obj.entry(off_key.to_string()).or_insert(val);
+                }
+            }
             obj.insert("energy-kcal_100g".to_string(), json!(params.calories));
         } else {
             nutriments = json!({"energy-kcal_100g": params.calories});