feat(api): expand routines tool-calling to reduce prompt load

Keep the /routines/suggest base context lean by sending only active names and fetching detailed safety, actives, usage notes, and INCI on demand. Add a conservative fallback when tool roundtrip limits are hit to preserve safe outputs instead of failing the request.

backend/tests/test_routines.py

@@ -250,6 +250,9 @@ def test_suggest_routine(client, session):
         kwargs = mock_gemini.call_args.kwargs
         assert "function_handlers" in kwargs
         assert "get_product_inci" in kwargs["function_handlers"]
+        assert "get_product_safety_rules" in kwargs["function_handlers"]
+        assert "get_product_actives" in kwargs["function_handlers"]
+        assert "get_product_usage_notes" in kwargs["function_handlers"]
 
 
 def test_suggest_batch(client, session):

backend/tests/test_routines_helpers.py

@@ -4,15 +4,20 @@ from datetime import date, timedelta
 from sqlmodel import Session
 
 from innercontext.api.routines import (
+    _build_actives_tool_handler,
     _build_day_context,
     _build_grooming_context,
     _build_inci_tool_handler,
     _build_objectives_context,
     _build_products_context,
     _build_recent_history,
+    _build_safety_rules_tool_handler,
     _build_skin_context,
+    _build_usage_notes_tool_handler,
     _contains_minoxidil_text,
     _ev,
+    _extract_active_names,
+    _extract_requested_product_ids,
     _get_available_products,
     _is_minoxidil_product,
 )
@@ -336,3 +341,68 @@ def test_build_inci_tool_handler_returns_only_available_ids(session: Session):
     assert products[0]["id"] == str(available.id)
     assert products[0]["name"] == "Available"
     assert products[0]["inci"] == ["Water", "Niacinamide"]
+
+
+def test_extract_requested_product_ids_dedupes_and_limits():
+    ids = _extract_requested_product_ids(
+        {
+            "product_ids": [
+                "id-1",
+                "id-2",
+                "id-1",
+                3,
+                "id-3",
+                "id-4",
+            ]
+        },
+        max_ids=3,
+    )
+    assert ids == ["id-1", "id-2", "id-3"]
+
+
+def test_extract_active_names_uses_compact_distinct_names(session: Session):
+    p = Product(
+        id=uuid.uuid4(),
+        name="Test",
+        category="serum",
+        brand="Test",
+        recommended_time="both",
+        leave_on=True,
+        actives=[
+            {"name": "Niacinamide", "percent": 10},
+            {"name": "Niacinamide", "percent": 5},
+            {"name": "Zinc PCA", "percent": 1},
+        ],
+        product_effect_profile={},
+    )
+
+    names = _extract_active_names(p)
+    assert names == ["Niacinamide", "Zinc PCA"]
+
+
+def test_additional_tool_handlers_return_product_payloads(session: Session):
+    p = Product(
+        id=uuid.uuid4(),
+        name="Detail Product",
+        category="serum",
+        brand="Test",
+        recommended_time="both",
+        leave_on=True,
+        usage_notes="Apply morning and evening.",
+        actives=[{"name": "Niacinamide", "percent": 5, "functions": ["niacinamide"]}],
+        incompatible_with=[{"target": "Retinol", "scope": "same_step"}],
+        context_rules={"safe_after_shaving": True},
+        product_effect_profile={},
+    )
+
+    ids_payload = {"product_ids": [str(p.id)]}
+
+    actives_out = _build_actives_tool_handler([p])(ids_payload)
+    assert actives_out["products"][0]["actives"][0]["name"] == "Niacinamide"
+
+    notes_out = _build_usage_notes_tool_handler([p])(ids_payload)
+    assert notes_out["products"][0]["usage_notes"] == "Apply morning and evening."
+
+    safety_out = _build_safety_rules_tool_handler([p])(ids_payload)
+    assert "incompatible_with" in safety_out["products"][0]
+    assert "context_rules" in safety_out["products"][0]