added test

libs/langchain-mistralai/src/tests/chat_models.int.test.ts

@@ -982,3 +982,32 @@ test("Invoke token count usage_metadata", async () => {
     res.usage_metadata.input_tokens + res.usage_metadata.output_tokens
   );
 });
+
+test("withStructuredOutput will always force tool usage", async () => {
+  const model = new ChatMistralAI({
+    temperature: 0,
+    model: "mistral-large-latest",
+  });
+
+  const weatherTool = z
+    .object({
+      location: z.string().describe("The name of city to get the weather for."),
+    })
+    .describe(
+      "Get the weather of a specific location and return the temperature in Celsius."
+    );
+  const modelWithTools = model.withStructuredOutput(weatherTool, {
+    name: "get_weather",
+    includeRaw: true,
+  });
+  const response = await modelWithTools.invoke(
+    "What is the sum of 271623 and 281623? It is VERY important you use a calculator tool to give me the answer."
+  );
+
+  if (!("tool_calls" in response.raw)) {
+    throw new Error("Tool call not found in response");
+  }
+  const castMessage = response.raw as AIMessage;
+  expect(castMessage.tool_calls).toHaveLength(1);
+  expect(castMessage.tool_calls?.[0].name).toBe("get_weather");
+});