diff --git a/invariant/analyzer/language/scope.py b/invariant/analyzer/language/scope.py
index 5f10453..f1584e7 100644
--- a/invariant/analyzer/language/scope.py
+++ b/invariant/analyzer/language/scope.py
@@ -30,6 +30,7 @@
     "sum",
     "print",
     "tuple",
+    "tool_call",
     "text",
     "image",
 ]
diff --git a/invariant/analyzer/stdlib/invariant/builtins.py b/invariant/analyzer/stdlib/invariant/builtins.py
index 7012138..141150c 100644
--- a/invariant/analyzer/stdlib/invariant/builtins.py
+++ b/invariant/analyzer/stdlib/invariant/builtins.py
@@ -91,3 +91,19 @@ def tuple(*args, **kwargs):
     Creates a tuple from the given arguments.
     """
     return py_builtins.tuple(*args, **kwargs)
+
+
+def tool_call(tool_output: ToolOutput, *args, **kwargs) -> ToolCall:
+    """
+    Gets the tool call object from a tool output.
+
+    Args:
+        tool_output: A ToolOutput object.
+
+    Returns:
+        The ToolCall object that corresponds to the tool call in the tool output.
+    """
+    if not isinstance(tool_output, ToolOutput):
+        raise ValueError("tool_output argument must be a ToolOutput.")
+
+    return tool_output._tool_call
diff --git a/invariant/tests/analyzer/test_builtins.py b/invariant/tests/analyzer/test_builtins.py
new file mode 100644
index 0000000..a334d65
--- /dev/null
+++ b/invariant/tests/analyzer/test_builtins.py
@@ -0,0 +1,36 @@
+import unittest
+
+from invariant.analyzer import Policy
+from invariant.analyzer.traces import assistant, tool, tool_call, user
+
+
+class TestBuiltins(unittest.TestCase):
+    def test_tool_call_name(self):
+        policy = Policy.from_string("""
+        raise "error" if:
+            (tool_output: ToolOutput)
+            tool_call(tool_output).function.name == "some_tool"
+        """)
+
+        trace = [
+            user("What is the result of something?"),
+            assistant(None, tool_call("1", "some_tool", {})),
+            tool("1", "some_output"),
+        ]
+        result = policy.analyze(trace)
+        assert len(result.errors) == 1
+
+    def test_tool_call_name_no_match(self):
+        policy = Policy.from_string("""
+        raise "error" if:
+            (tool_output: ToolOutput)
+            tool_call(tool_output).function.name == "some_tool"
+        """)
+
+        trace = [
+            user("What is the result of something?"),
+            assistant(None, tool_call("1", "some_other_tool", {})),
+            tool("1", "some_output"),
+        ]
+        result = policy.analyze(trace)
+        assert len(result.errors) == 0