diff --git a/common/jinja/jinja-value.cpp b/common/jinja/jinja-value.cpp
index 5a515fc8e4..6c3d9249b3 100644
--- a/common/jinja/jinja-value.cpp
+++ b/common/jinja/jinja-value.cpp
@@ -165,6 +165,11 @@ const func_builtins & global_builtins() {
             }
             return out;
         }},
+        {"tojson", [](const func_args & args) -> value {
+            args.ensure_count(1);
+            // placeholder implementation
+            return mk_val<value_string>("TODO: to_json output");
+        }},
 
         // tests
         {"test_is_boolean", test_type_fn<value_bool>},
@@ -646,7 +651,12 @@ const func_builtins & value_object_t::get_builtins() const {
             }
             return result;
         }},
-        {{"dictsort"}, [](const func_args & args) -> value {
+        {"tojson", [](const func_args & args) -> value {
+            args.ensure_vals<value_object>();
+            // use global to_json
+            return global_builtins().at("tojson")(args);
+        }},
+        {"dictsort", [](const func_args & args) -> value {
             // no-op
             args.ensure_vals<value_object>();
             return args.args[0];
diff --git a/common/jinja/jinja-vm.cpp b/common/jinja/jinja-vm.cpp
index ed98f1d050..d6958a54c9 100644
--- a/common/jinja/jinja-vm.cpp
+++ b/common/jinja/jinja-vm.cpp
@@ -312,10 +312,19 @@ value test_expression::execute_impl(context & ctx) {
         throw std::runtime_error("Unknown test '" + test_id + "'");
     }
 
+    value input = operand->execute(ctx);
+
     func_args args(ctx);
-    args.args.push_back(operand->execute(ctx));
+    args.args.push_back(input);
     auto res = it->second(args);
 
+    // hack: allow type inference
+    if (test_id == "defined" || test_id == "undefined" || test_id == "none") {
+        ctx.mark_known_type(input, inferred_type::optional);
+    } else if (test_id == "string") {
+        ctx.mark_known_type(input, inferred_type::string);
+    }
+
     if (negate) {
         return mk_val<value_bool>(!res->as_bool());
     } else {
diff --git a/common/jinja/jinja-vm.h b/common/jinja/jinja-vm.h
index bb24abad96..0ac2e5f16a 100644
--- a/common/jinja/jinja-vm.h
+++ b/common/jinja/jinja-vm.h
@@ -105,8 +105,9 @@ public:
         if (is_val<value_object>(val)) {
             auto & obj = val->as_object();
             for (const auto & pair : obj) {
-                flatten_globals[pair.first] = pair.second;
-                set_flattened_global_recursively(pair.first, pair.second);
+                std::string child_path = path + "." + pair.first;
+                flatten_globals[child_path] = pair.second;
+                set_flattened_global_recursively(child_path, pair.second);
             }
         } else if (is_val<value_array>(val)) {
             auto & arr = val->as_array();
diff --git a/tests/test-chat-jinja.cpp b/tests/test-chat-jinja.cpp
index 39ce9fed00..c205b150cf 100644
--- a/tests/test-chat-jinja.cpp
+++ b/tests/test-chat-jinja.cpp
@@ -123,6 +123,21 @@ void run_single(std::string contents) {
             {
                 "role": "assistant",
                 "content": {"__input__": "I am fine, thank you!"}
+            },
+            {
+                "role": "assistant",
+                "content": "Calling weather tool.",
+                "tool_calls": [
+                    {
+                        "function": {
+                            "name": "get_weather",
+                            "arguments": {
+                                "location": "New York",
+                                "unit": "celsius"
+                            }
+                        }
+                    }
+                ]
             }
         ],
         "bos_token": "<s>",