Harden MCP article and weight workflows

mcp_server.py

@@ -6,6 +6,7 @@ from typing import Any
 
 from rollcalc_mcp_tools import (
     analyze_transport_capacity_result,
+    calculate_material_weight_result,
     calculate_roll_diameter_result,
     get_article_result,
     search_articles_result,
@@ -29,9 +30,22 @@ def create_server() -> Any:
 
     @server.tool()
     def search_articles(query: str) -> dict[str, Any]:
-        """Use search_articles when the user identifies a RollCalc product by name, family, designation, or descriptive article text instead of an exact article number. Do not guess or invent an article number: results are deterministic candidates from the RollCalc article master data. For an exact article number, use get_article -> calculate_roll_diameter -> optionally analyze_transport_capacity. For a product name, use search_articles first. Only when total_matches is exactly 1 may you use that candidate's exact article_number and continue through get_article and the requested workflow. When multiple candidates are returned, do NOT select the first or highest-ranked candidate and do not calculate yet: present relevant candidates with their article numbers, distinguishing names, and production_site when supplied; ask the user which article number is intended, then stop until they select it. Ranking/order expresses relevance only and never authorizes automatic selection. If no candidate is returned, say that no matching RollCalc article was found, ask for a more specific designation or article number, and do not invent an article. production_site=Malaysia is descriptive metadata only: it does not imply Bentofix, Bento 2, or any production machine."""
+        """Use search_articles when the user identifies a RollCalc product by name, family, designation, or descriptive article text instead of an exact article number. Do not guess or invent an article number: results are deterministic retrieval candidates from the RollCalc article master data, not product recommendations. For an exact article number, use get_article -> calculate_roll_diameter -> optionally analyze_transport_capacity. For a product name, use search_articles first. Only when total_matches is exactly 1 may you use that candidate's exact article_number and continue through get_article and the requested workflow. When multiple plausible candidates are returned, do NOT select the first or highest-ranked candidate, do not treat ranking as permission to choose, and do not calculate yet: present relevant candidates with their article numbers, distinguishing names, and production_site when supplied; ask the user which article number is intended, then stop until they select it. Ranking/order expresses retrieval relevance only and never authorizes automatic selection. If no candidate is returned, say that no matching RollCalc article was found, ask for a more specific designation or article number, and do not invent an article. production_site=Malaysia is descriptive metadata only: it does not imply Bentofix, Bento 2, or any production machine."""
         return search_articles_result(query)
 
+    @server.tool()
+    def calculate_material_weight(
+        roll_length_m: float,
+        width_m: float,
+        area_weight_g_m2: float,
+    ) -> dict[str, Any]:
+        """Calculate deterministic material-only roll weight from roll_length_m (m), width_m (m), and area_weight_g_m2 (g/m²). Use this when those inputs are known but core diameter is unknown or not needed. It does not require, accept, infer, or default a core diameter; never invent a standard core. The result excludes any core weight and cannot provide roll diameter or a core-inclusive total weight. For roll diameter, use calculate_roll_diameter only with a known positive core diameter."""
+        return calculate_material_weight_result(
+            roll_length_m=roll_length_m,
+            width_m=width_m,
+            area_weight_g_m2=area_weight_g_m2,
+        )
+
     @server.tool()
     def calculate_roll_diameter(
         roll_length_m: float | None = None,
@@ -46,7 +60,7 @@ def create_server() -> Any:
         category: str | None = None,
         production_site: str | None = None,
     ) -> dict[str, Any]:
-        """Calculate roll diameter and weight for one roll. roll_length_m is the material length on one roll in m; core_diameter_mm, thickness_mm, and thickness_stddev_mm are mm; width_m is m; and area_weight_g_m2 is g/m². Resolve an article or provide applicable manual material inputs. This MCP tool always returns roll_weight_kg when the required width_m and area_weight_g_m2 inputs are available. On success, transport_roll_inputs contains the browser-equivalent transport values; pass that bundle's fields unchanged to analyze_transport_capacity."""
+        """Calculate roll diameter and weight for one roll. roll_length_m is the material length on one roll in m; core_diameter_mm, thickness_mm, and thickness_stddev_mm are mm; width_m is m; and area_weight_g_m2 is g/m². Roll diameter requires a known positive core diameter: do not infer or default one. If only material weight is needed and the core is unknown, call calculate_material_weight instead; it returns material-only weight, not a diameter or core-inclusive total. On success, transport_roll_inputs contains the browser-equivalent transport values; pass that bundle's fields unchanged to analyze_transport_capacity."""
         return calculate_roll_diameter_result(
             article_number=article_number,
             article_name_hint=article_name_hint,