langchain-ai/langgraph · error · ValueError

Invalid input to ToolNode. Tool {name} requires graph state

Error message

Invalid input to ToolNode. Tool {name} requires graph state dict as input.

What it means

Error "Invalid input to ToolNode. Tool {name} requires graph state dict as input." thrown in langchain-ai/langgraph.

Source

Thrown at libs/prebuilt/langgraph/prebuilt/tool_node.py:1387

            # Handle list state by converting to dict
            if isinstance(state, list):
                required_fields = list(injected.state.values())
                if (
                    len(required_fields) == 1
                    and required_fields[0] == self._messages_key
                ) or required_fields[0] is None:
                    state = {self._messages_key: state}
                else:
                    err_msg = (
                        f"Invalid input to ToolNode. Tool {tool_call['name']} requires "
                        f"graph state dict as input."
                    )
                    if any(state_field for state_field in injected.state.values()):
                        required_fields_str = ", ".join(f for f in required_fields if f)
                        err_msg += (
                            f" State should contain fields {required_fields_str}."
                        )
                    raise ValueError(err_msg)

            # Extract state values
            if isinstance(state, dict):
                for tool_arg, state_field in injected.state.items():
                    if not state_field:
                        injected_args[tool_arg] = state
                    elif state_field in state:
                        injected_args[tool_arg] = state[state_field]
                    elif tool_arg not in injected._optional_state_args:
                        raise KeyError(state_field)
            else:
                for tool_arg, state_field in injected.state.items():
                    if not state_field:
                        injected_args[tool_arg] = state
                    elif hasattr(state, state_field):
                        injected_args[tool_arg] = getattr(state, state_field)
                    elif tool_arg not in injected._optional_state_args:
                        raise AttributeError(state_field)

View on GitHub (pinned to 38031739e5)

When it happens

Trigger: Thrown at libs/prebuilt/langgraph/prebuilt/tool_node.py:1387 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of langchain-ai/langgraph@38031739e5 (2026-08-26). Data as JSON: /api/errors/b124d5e53afd81dd. Report an issue: GitHub.