feat: make tools parameter optional in function signatures

The tools parameter is now optional across all relevant function signatures, allowing calls without explicitly passing tools. This change simplifies the API by defaulting to no tools when not specified, reducing boilerplate for common use cases.

chat.h

@@ -51,7 +51,9 @@ char *chat_json(const char *role, const char *message) {
 
   if (role != NULL && message != NULL) {
     message_add(role, message);
-    json_object_object_add(root_object, "tools", tools_descriptions());
+    if(use_tools()){
+        json_object_object_add(root_object, "tools", tools_descriptions());
+    }
   }
 
   json_object_object_add(root_object, "messages", message_list());

r.h

@@ -32,6 +32,26 @@ char *_model = NULL;
 #define DB_FILE "~/.r.db"
 #define PROMPT_TEMPERATURE 0.1
 
+
+bool use_tools(){
+    if(getenv("R_USE_TOOLS") != NULL){
+        const char *value = getenv("R_USE_TOOLS");
+        if (!strcmp(value, "true")) {
+            return true;
+        }
+        if (!strcmp(value, "false")) {
+            return false;
+        }
+        if (!strcmp(value, "1")) {
+            return true;
+        }
+        if (!strcmp(value, "0")) {
+            return false;
+        }
+    }
+    return true;
+}
+
 char * get_env_system_message(){
     if (getenv("R_SYSTEM_MESSAGE") != NULL) {
         return strdup(getenv("R_SYSTEM_MESSAGE"));