refactor: enhance response serialization and improve schema generation error handling

Author: rpanackal

foundation-models/openai/src/main/java/com/sap/ai/sdk/foundationmodels/openai/OpenAiChatCompletionResponse.java

@@ -4,6 +4,7 @@
 import static lombok.AccessLevel.NONE;
 import static lombok.AccessLevel.PACKAGE;
 
+import com.fasterxml.jackson.core.JsonProcessingException;
 import com.google.common.annotations.Beta;
 import com.sap.ai.sdk.foundationmodels.openai.generated.model.CompletionUsage;
 import com.sap.ai.sdk.foundationmodels.openai.generated.model.CreateChatCompletionResponse;
@@ -107,7 +108,14 @@ public <T, R> List<OpenAiToolMessage> executeTools(List<OpenAiTool<T, R>> tools)
           if (tool.getName().equals(functionCall.getName())) {
             T arguments = functionCall.getArgumentsAsObject(tool);
             R response = tool.execute(arguments);
-            toolMessages.add(OpenAiMessage.tool(response.toString(), functionCall.getId()));
+
+            String serializedResponse;
+            try {
+              serializedResponse = OpenAiUtils.getOpenAiObjectMapper().writeValueAsString(response);
+            } catch (JsonProcessingException e) {
+              throw new IllegalArgumentException(e);
+            }
+            toolMessages.add(OpenAiMessage.tool(serializedResponse, functionCall.getId()));
           }
         }
       }

foundation-models/openai/src/main/java/com/sap/ai/sdk/foundationmodels/openai/OpenAiTool.java

@@ -97,11 +97,9 @@ ChatCompletionTool createChatCompletionTool() {
     final var objectMapper = new ObjectMapper();
     JsonSchema schema = null;
     try {
-      schema =
-          new JsonSchemaGenerator(objectMapper)
-              .generateSchema(new TypeReference<T>() {}.getClass());
+      schema = new JsonSchemaGenerator(objectMapper).generateSchema(getRequestClass());
     } catch (JsonMappingException e) {
-      throw new IllegalArgumentException("Could not generate schema for " + name, e);
+      throw new IllegalArgumentException("Could not generate schema for " + getRequestClass(), e);
     }
 
     final var schemaMap =