huggingface/smolagents · error · ValueError

Each tool or managed_agent should have a unique name! You pa

Error message

Each tool or managed_agent should have a unique name! You passed these duplicate names: {[name for name in tool_and_managed_agent_names if tool_and_managed_agent_names.count(name) > 1]}

What it means

Every tool and managed agent attached to an agent (plus the agent's own name) must have a unique name, because the framework dispatches tool calls and generates code referencing them by name. _validate_tools_and_managed_agents raises ValueError listing the duplicates found.

Source

Thrown at src/smolagents/agents.py:411

        self.tools = {tool.name: tool for tool in tools}
        if add_base_tools:
            self.tools.update(
                {
                    name: cls()
                    for name, cls in TOOL_MAPPING.items()
                    if name != "python_interpreter" or self.__class__.__name__ == "ToolCallingAgent"
                }
            )
        self.tools.setdefault("final_answer", FinalAnswerTool())

    def _validate_tools_and_managed_agents(self, tools, managed_agents):
        tool_and_managed_agent_names = [tool.name for tool in tools]
        if managed_agents is not None:
            tool_and_managed_agent_names += [agent.name for agent in managed_agents]
        if self.name:
            tool_and_managed_agent_names.append(self.name)
        if len(tool_and_managed_agent_names) != len(set(tool_and_managed_agent_names)):
            raise ValueError(
                "Each tool or managed_agent should have a unique name! You passed these duplicate names: "
                f"{[name for name in tool_and_managed_agent_names if tool_and_managed_agent_names.count(name) > 1]}"
            )

    def _setup_step_callbacks(self, step_callbacks):
        # Initialize step callbacks registry
        self.step_callbacks = CallbackRegistry()
        if step_callbacks:
            # Register callbacks list only for ActionStep for backward compatibility
            if isinstance(step_callbacks, list):
                for callback in step_callbacks:
                    self.step_callbacks.register(ActionStep, callback)
            # Register callbacks dict for specific step classes
            elif isinstance(step_callbacks, dict):
                for step_cls, callbacks in step_callbacks.items():
                    if not isinstance(callbacks, list):
                        callbacks = [callbacks]
                    for callback in callbacks:

View on GitHub (pinned to 30bb116109)

Solutions

1. Give each tool/agent a distinct .name (subclass or set instance attribute before passing)
2. Remove duplicated tools from the list; if using ToolCollection, don't also pass the same tools individually
3. Rename the managed agent or the parent agent if they collide

Example fix

# before
search1 = DuckDuckGoSearchTool()
search2 = DuckDuckGoSearchTool()  # both default to name='web_search'
agent = CodeAgent(tools=[search1, search2], llm_engine=llm)

# after
search2 = DuckDuckGoSearchTool(name="web_search_backup")
agent = CodeAgent(tools=[search1, search2], llm_engine=llm)

names = [t.name for t in tools] + [a.name for a in managed_agents or []] + [agent_name]
assert len(names) == len(set(names)), f"duplicates: {[n for n in set(names) if names.count(n) > 1]}"
agent = CodeAgent(tools=tools, managed_agents=managed_agents, ...)

When it happens

Trigger: Passing tools=[t1, t2] where t1.name == t2.name; adding a managed agent whose name matches a tool name; a managed agent sharing the parent agent's self.name.

Common situations: Instantiating two tools of the same class without overriding .name (e.g. two DuckDuckGoSearchTool() instances); wrapping the same tool in ToolCollection and also passing it directly; giving a managed agent the same name as the orchestrating agent.

Related errors

• Cannot specify both 'messages' and 'steps' parameters. Use '
• Agent name '{name}' must be a valid Python identifier and no
• step_callbacks must be a list or a dict
• Tool {tool_name} is not recognized either as a default tool
• Error during jinja template rendering: {type(e).__name__}: {

AI-assisted analysis of huggingface/smolagents@30bb116109 (2026-08-28). Data as JSON: /api/errors/088fb6701e087343. Report an issue: GitHub.