[agents] remove agents 🧹 (#37368)

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Joao Gante
2025-04-11 18:42:37 +01:00
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sections:
- sections:
- local: main_classes/agent
title: Agents and Tools
- local: model_doc/auto
title: Auto Classes
- local: main_classes/backbones

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> [!WARNING]
> Agents and tools are being spun out into the standalone [smolagents](https://huggingface.co/docs/smolagents/index) library. These docs will be deprecated in the future!
# Agents
[[open-in-colab]]
An agent is a system where a large language model (LLM) can execute more complex tasks through *planning* and using *tools*.
- Planning helps a LLM reason its way through a task by breaking it down into smaller subtasks. For example, [`CodeAgent`] plans a series of actions to take and then generates Python code to execute all the actions at once.
Another planning method is by self-reflection and refinement of its previous actions to improve its performance. The [`ReactJsonAgent`] is an example of this type of planning, and it's based on the [ReAct](https://hf.co/papers/2210.03629) framework. This agent plans and executes actions one at a time based on the feedback it receives from each action.
- Tools give a LLM access to external functions or APIs that it can use to help it complete a task. For example, [gradio-tools](https://github.com/freddyaboulton/gradio-tools) gives a LLM access to any of the [Gradio](https://www.gradio.app/) apps available on Hugging Face [Spaces](https://hf.co/spaces). These apps can be used for a wide range of tasks such as image generation, video generation, audio transcription, and more.
To use agents in Transformers, make sure you have the extra `agents` dependencies installed.
```bash
!pip install transformers[agents]
```
Create an agent instance (refer to the [Agents](./main_classes/agent#agents) API for supported agents in Transformers) and a list of tools available for it to use, then [`~ReactAgent.run`] the agent on your task. The example below demonstrates how a ReAct agent reasons through a task.
```py
from transformers import ReactCodeAgent
agent = ReactCodeAgent(tools=[])
agent.run(
"How many more blocks (also denoted as layers) in BERT base encoder than the encoder from the architecture proposed in Attention is All You Need?",
)
```
```bash
======== New task ========
How many more blocks (also denoted as layers) in BERT base encoder than the encoder from the architecture proposed in Attention is All You Need?
==== Agent is executing the code below:
bert_layers = 12 # BERT base encoder has 12 layers
attention_layers = 6 # Encoder in Attention is All You Need has 6 layers
layer_diff = bert_layers - attention_layers
print("The difference in layers between BERT base encoder and Attention is All You Need is", layer_diff)
====
Print outputs:
The difference in layers between BERT base encoder and Attention is All You Need is 6
==== Agent is executing the code below:
final_answer("BERT base encoder has {} more layers than the encoder from Attention is All You Need.".format(layer_diff))
====
Print outputs:
>>> Final answer:
BERT base encoder has 6 more layers than the encoder from Attention is All You Need.
```
This guide will walk you through in more detail how to initialize an agent.
## LLM
An agent uses a LLM to plan and execute a task; it is the engine that powers the agent. To choose and build your own LLM engine, you need a method that:
1. the input uses the [chat template](./chat_templating) format, `List[Dict[str, str]]`, and it returns a string
2. the LLM stops generating outputs when it encounters the sequences in `stop_sequences`
```py
def llm_engine(messages, stop_sequences=["Task"]) -> str:
response = client.chat_completion(messages, stop=stop_sequences, max_tokens=1000)
answer = response.choices[0].message.content
return answer
```
Next, initialize an engine to load a model. To run an agent locally, create a [`TransformersEngine`] to load a preinitialized [`Pipeline`].
However, you could also leverage Hugging Face's powerful inference infrastructure, [Inference API](https://hf.co/docs/api-inference/index) or [Inference Endpoints](https://hf.co/docs/inference-endpoints/index), to run your model. This is useful for loading larger models that are typically required for agentic behavior. In this case, load the [`HfApiEngine`] to run the agent.
The agent requires a list of tools it can use to complete a task. If you aren't using any additional tools, pass an empty list. The default tools provided by Transformers are loaded automatically, but you can optionally set `add_base_tools=True` to explicitly enable them.
<hfoptions id="engine">
<hfoption id="TransformersEngine">
```py
from transformers import AutoModelForCausalLM, AutoTokenizer, pipeline, TransformersEngine, CodeAgent
tokenizer = AutoTokenizer.from_pretrained("meta-llama/Llama-3.1-8B-Instruct")
model = AutoModelForCausalLM.from_pretrained("meta-llama/Llama-3.1-8B-Instruct").to("cuda")
pipeline = pipeline("text-generation", model=model, tokenizer=tokenizer)
llm_engine = TransformersEngine(pipeline)
agent = CodeAgent(tools=[], llm_engine=llm_engine)
agent.run(
"What causes bread to rise?",
)
```
</hfoption>
<hfoption id="HfApiEngine">
```py
from transformers import CodeAgent, HfApiEngine
llm_engine = HfApiEngine(model="meta-llama/Meta-Llama-3-70B-Instruct")
agent = CodeAgent(tools=[], llm_engine=llm_engine)
agent.run(
"Could you translate this sentence from French, say it out loud and return the audio.",
sentence="Où est la boulangerie la plus proche?",
)
```
</hfoption>
</hfoptions>
The agent supports [constrained generation](https://hf.co/docs/text-generation-inference/conceptual/guidance) for generating outputs according to a specific structure with the `grammar` parameter. The `grammar` parameter should be specified in the `llm_engine` method or you can set it when initializing an agent.
Lastly, an agent accepts additional inputs such as text and audio. In the [`HfApiEngine`] example above, the agent accepted a sentence to translate. But you could also pass a path to a local or remote file for the agent to access. The example below demonstrates how to pass a path to an audio file.
```py
from transformers import ReactCodeAgent
agent = ReactCodeAgent(tools=[], llm_engine=llm_engine)
agent.run("Why doesn't he know many people in New York?", audio="https://huggingface.co/datasets/huggingface/documentation-images/resolve/main/transformers/recording.mp3")
```
## System prompt
A system prompt describes how an agent should behave, a description of the available tools, and the expected output format.
Tools are defined by the `<<tool_descriptions>>` token which is dynamically replaced during runtime with the actual tool. The tool description is derived from the tool name, description, inputs, output type, and a Jinja2 template. Refer to the [Tools](./tools) guide for more information about how to describe tools.
The example below is the system prompt for [`ReactCodeAgent`].
```py
You will be given a task to solve as best you can.
You have access to the following tools:
<<tool_descriptions>>
To solve the task, you must plan forward to proceed in a series of steps, in a cycle of 'Thought:', 'Code:', and 'Observation:' sequences.
At each step, in the 'Thought:' sequence, you should first explain your reasoning towards solving the task, then the tools that you want to use.
Then in the 'Code:' sequence, you should write the code in simple Python. The code sequence must end with '/End code' sequence.
During each intermediate step, you can use 'print()' to save whatever important information you will then need.
These print outputs will then be available in the 'Observation:' field, for using this information as input for the next step.
In the end you have to return a final answer using the `final_answer` tool.
Here are a few examples using notional tools:
---
{examples}
Above example were using notional tools that might not exist for you. You only have access to those tools:
<<tool_names>>
You also can perform computations in the python code you generate.
Always provide a 'Thought:' and a 'Code:\n```py' sequence ending with '```<end_code>' sequence. You MUST provide at least the 'Code:' sequence to move forward.
Remember to not perform too many operations in a single code block! You should split the task into intermediate code blocks.
Print results at the end of each step to save the intermediate results. Then use final_answer() to return the final result.
Remember to make sure that variables you use are all defined.
Now Begin!
```
The system prompt can be tailored to the intended task. For example, you can add a better explanation of the output format or you can overwrite the system prompt template entirely with your own custom system prompt as shown below.
> [!WARNING]
> If you're writing a custom system prompt, make sure to include `<<tool_descriptions>>` in the template so the agent is aware of the available tools.
```py
from transformers import ReactJsonAgent
from transformers.agents import PythonInterpreterTool
agent = ReactJsonAgent(tools=[PythonInterpreterTool()], system_prompt="{your_custom_prompt}")
```
## Code execution
For safety, only the tools you provide (and the default Transformers tools) and the `print` function are executed. The interpreter doesn't allow importing modules that aren't on a safe list.
To import modules that aren't on the list, add them as a list to the `additional_authorized_imports` parameter when initializing an agent.
```py
from transformers import ReactCodeAgent
agent = ReactCodeAgent(tools=[], additional_authorized_imports=['requests', 'bs4'])
agent.run("Could you get me the title of the page at url 'https://huggingface.co/blog'?")
```
Code execution stops if a tool isn't on the safe list, it isn't authorized, or if the code generated by the agent returns a Python error.
> [!WARNING]
> A LLM can generate any arbitrary code that can be executed, so don't add any unsafe imports!
## Multi-agent
[Multi-agent](https://hf.co/papers/2308.08155) refers to multiple agents working together to solve a task. Performance is typically better because each agent is specialized for a particular subtask.
Multi-agents are created through a [`ManagedAgent`] class, where a *manager agent* oversees how other agents work together. The manager agent requires an agent and their name and description. These are added to the manager agents system prompt which lets it know how to call and use them.
The multi-agent example below creates a web search agent that is managed by another [`ReactCodeAgent`].
```py
from transformers.agents import ReactCodeAgent, HfApiEngine, DuckDuckGoSearchTool, ManagedAgent
llm_engine = HfApiEngine()
web_agent = ReactCodeAgent(tools=[DuckDuckGoSearchTool()], llm_engine=llm_engine)
managed_web_agent = ManagedAgent(
agent=web_agent,
name="web_search",
description="Runs web searches for you. Give it your query as an argument."
)
manager_agent = ReactCodeAgent(
tools=[], llm_engine=llm_engine, managed_agents=[managed_web_agent]
)
manager_agent.run("Who is the CEO of Hugging Face?")
```
## Gradio integration
[Gradio](https://www.gradio.app/) is a library for quickly creating and sharing machine learning apps. The [gradio.Chatbot](https://www.gradio.app/docs/gradio/chatbot) supports chatting with a Transformers agent with the [`stream_to_gradio`] function.
Load a tool and LLM with an agent, and then create a Gradio app. The key is to use [`stream_to_gradio`] to stream the agents messages and display how it's reasoning through a task.
```py
import gradio as gr
from transformers import (
load_tool,
ReactCodeAgent,
HfApiEngine,
stream_to_gradio,
)
# Import tool from Hub
image_generation_tool = load_tool("m-ric/text-to-image")
llm_engine = HfApiEngine("meta-llama/Meta-Llama-3-70B-Instruct")
# Initialize the agent with the image generation tool
agent = ReactCodeAgent(tools=[image_generation_tool], llm_engine=llm_engine)
def interact_with_agent(task):
messages = []
messages.append(gr.ChatMessage(role="user", content=task))
yield messages
for msg in stream_to_gradio(agent, task):
messages.append(msg)
yield messages + [
gr.ChatMessage(role="assistant", content="⏳ Task not finished yet!")
]
yield messages
with gr.Blocks() as demo:
text_input = gr.Textbox(lines=1, label="Chat Message", value="Make me a picture of the Statue of Liberty.")
submit = gr.Button("Run illustrator agent!")
chatbot = gr.Chatbot(
label="Agent",
type="messages",
avatar_images=(
None,
"https://em-content.zobj.net/source/twitter/53/robot-face_1f916.png",
),
)
submit.click(interact_with_agent, [text_input], [chatbot])
if __name__ == "__main__":
demo.launch()
```
## Troubleshoot
For a better idea of what is happening when you call an agent, it is always a good idea to check the system prompt template first.
```py
print(agent.system_prompt_template)
```
If the agent is behaving unexpectedly, remember to explain the task you want to perform as clearly as possible. Every [`~Agent.run`] is different and minor variations in your system prompt may yield completely different results.
To find out what happened after a run, check the following agent attributes.
- `agent.logs` stores the finegrained agent logs. At every step of the agents run, everything is stored in a dictionary and appended to `agent.logs`.
- `agent.write_inner_memory_from_logs` only stores a high-level overview of the agents run. For example, at each step, it stores the LLM output as a message and the tool call output as a separate message. Not every detail from a step is transcripted by `write_inner_memory_from_logs`.
## Resources
Learn more about ReAct agents in the [Open-source LLMs as LangChain Agents](https://hf.co/blog/open-source-llms-as-agents) blog post.
> Agents and tools were spun out into the standalone [smolagents](https://huggingface.co/docs/smolagents/index) library. They were removed from `transformers` in v4.52.

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specific language governing permissions and limitations under the License.
⚠️ Note that this file is in Markdown but contain specific syntax for our doc-builder (similar to MDX) that may not be
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-->
# Agents & Tools
<Tip warning={true}>
Transformers Agents is an experimental API which is subject to change at any time. Results returned by the agents
can vary as the APIs or underlying models are prone to change.
</Tip>
To learn more about agents and tools make sure to read the [introductory guide](../transformers_agents). This page
contains the API docs for the underlying classes.
## Agents
We provide two types of agents, based on the main [`Agent`] class:
- [`CodeAgent`] acts in one shot, generating code to solve the task, then executes it at once.
- [`ReactAgent`] acts step by step, each step consisting of one thought, then one tool call and execution. It has two classes:
- [`ReactJsonAgent`] writes its tool calls in JSON.
- [`ReactCodeAgent`] writes its tool calls in Python code.
### Agent
[[autodoc]] Agent
### CodeAgent
[[autodoc]] CodeAgent
### React agents
[[autodoc]] ReactAgent
[[autodoc]] ReactJsonAgent
[[autodoc]] ReactCodeAgent
### ManagedAgent
[[autodoc]] ManagedAgent
## Tools
### load_tool
[[autodoc]] load_tool
### tool
[[autodoc]] tool
### Tool
[[autodoc]] Tool
### Toolbox
[[autodoc]] Toolbox
### PipelineTool
[[autodoc]] PipelineTool
### launch_gradio_demo
[[autodoc]] launch_gradio_demo
### stream_to_gradio
[[autodoc]] stream_to_gradio
### ToolCollection
[[autodoc]] ToolCollection
## Engines
You're free to create and use your own engines to be usable by the Agents framework.
These engines have the following specification:
1. Follow the [messages format](../chat_templating.md) for its input (`List[Dict[str, str]]`) and return a string.
2. Stop generating outputs *before* the sequences passed in the argument `stop_sequences`
### TransformersEngine
For convenience, we have added a `TransformersEngine` that implements the points above, taking a pre-initialized `Pipeline` as input.
```python
>>> from transformers import AutoModelForCausalLM, AutoTokenizer, pipeline, TransformersEngine
>>> model_name = "HuggingFaceTB/SmolLM-135M-Instruct"
>>> tokenizer = AutoTokenizer.from_pretrained(model_name)
>>> model = AutoModelForCausalLM.from_pretrained(model_name)
>>> pipe = pipeline("text-generation", model=model, tokenizer=tokenizer)
>>> engine = TransformersEngine(pipe)
>>> engine([{"role": "user", "content": "Ok!"}], stop_sequences=["great"])
"What a "
```
[[autodoc]] TransformersEngine
### HfApiEngine
The `HfApiEngine` is an engine that wraps an [HF Inference API](https://huggingface.co/docs/api-inference/index) client for the execution of the LLM.
```python
>>> from transformers import HfApiEngine
>>> messages = [
... {"role": "user", "content": "Hello, how are you?"},
... {"role": "assistant", "content": "I'm doing great. How can I help you today?"},
... {"role": "user", "content": "No need to help, take it easy."},
... ]
>>> HfApiEngine()(messages, stop_sequences=["conversation"])
"That's very kind of you to say! It's always nice to have a relaxed "
```
[[autodoc]] HfApiEngine
## Agent Types
Agents can handle any type of object in-between tools; tools, being completely multimodal, can accept and return
text, image, audio, video, among other types. In order to increase compatibility between tools, as well as to
correctly render these returns in ipython (jupyter, colab, ipython notebooks, ...), we implement wrapper classes
around these types.
The wrapped objects should continue behaving as initially; a text object should still behave as a string, an image
object should still behave as a `PIL.Image`.
These types have three specific purposes:
- Calling `to_raw` on the type should return the underlying object
- Calling `to_string` on the type should return the object as a string: that can be the string in case of an `AgentText`
but will be the path of the serialized version of the object in other instances
- Displaying it in an ipython kernel should display the object correctly
### AgentText
[[autodoc]] transformers.agents.agent_types.AgentText
### AgentImage
[[autodoc]] transformers.agents.agent_types.AgentImage
### AgentAudio
[[autodoc]] transformers.agents.agent_types.AgentAudio

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> [!WARNING]
> Agents and tools are being spun out into the standalone [smolagents](https://huggingface.co/docs/smolagents/index) library. These docs will be deprecated in the future!
# Tools
A tool is a function an agent can use to complete a task. Depending on your task, a tool can perform a web search, answer questions about a document, transcribe speech to text, and much more.
Transformers provides a default set of tools for agents. These include the tools mentioned above as well as image question answering, text-to-speech, translation, and a Python code interpreter that executes the Python code generated by a LLM in a secure environment.
Set `add_base_tools=True` to enable this default set of tools. The `tools` parameter is for adding additional tools. Leave the list empty if you aren't planning on adding any other tools to the toolbox.
```py
from transformers import ReactCodeAgent
agent = ReactCodeAgent(tools=[], add_base_tools=True)
```
You could also manually load a tool with [`load_tool`].
```py
from transformers import load_tool, ReactCodeAgent
tool = load_tool("text-to-speech")
audio = tool("This is a text-to-speech tool")
agent = ReactCodeAgent(tools=[audio])
```
This guide will help you learn how to create your own tools and manage an agents toolbox.
## Create a new tool
You can create any tool you can dream of to empower an agent. The example in this section creates a tool that returns the most downloaded model for a task from the Hub, and the code for it is shown below.
```py
from huggingface_hub import list_models
task = "text-classification"
model = next(iter(list_models(filter=task, sort="downloads", direction=-1)))
print(model.id)
```
There are two ways you can create a tool, using a decorator or a superclass.
### Tool decorator
A fast and simple way to create a tool is to add the `@tool` decorator.
Convert the code above into a tool by wrapping it in a function and adding the `@tool` decorator. The function needs:
- A clear name that describes what the tool does, `model_download_counter`.
- Type hints for the input and output (`str`).
- A description that describes the tool in more detail and its arguments. This description is incorporated in the agents system prompt. It tells the agent *how* to use the tool, so try to make it as clear as possible!
```py
from transformers import tool
@tool
def model_download_counter(task: str) -> str:
"""
This is a tool that returns the checkpoint name of the most downloaded model for a task from the Hugging Face Hub.
Args:
task: The task to retrieve the most downloaded model from.
"""
model = next(iter(list_models(filter=task, sort="downloads", direction=-1)))
return model.id
```
Pass the `model_download_counter` tool to the agents `tools` parameter to use it.
```py
from transformers import CodeAgent
agent = CodeAgent(tools=[model_download_counter], add_base_tools=True)
agent.run(
"Can you give me the name of the model that has the most downloads on the 'text-to-video' task on the Hugging Face Hub?"
)
```
### Tool superclass
Inheritance allows you to customize the [`Tool`] superclass or build a tool much more flexibly and comprehensively. This example will show you how to build the same `model_download_counter` tool as a [`Tool`] class.
The [`Tool`] class needs:
- A clear name that describes what the tool does, `model_download_counter`.
- A description that describes the tool in more detail and its arguments. This description is incorporated in the agents system prompt. It tells the agent *how* to use the tool, so try to make it as clear as possible!
- An `inputs` attribute that describes the input type. This is a dictionary with the keys, `type` and `description`.
- An `outputs` attribute that describes the output type.
- A `forward` method containing the code to be executed when the tool is called.
Write the following code below to a file named `model_download.py`.
```py
from transformers import Tool
from huggingface_hub import list_models
class HFModelDownloadsTool(Tool):
name = "model_download_counter"
description = """
This is a tool that returns the checkpoint name of the most downloaded model for a task from the Hugging Face Hub."""
inputs = {
"task": {
"type": "string",
"description": "the task category (such as text-classification, depth-estimation, etc)",
}
}
output_type = "string"
def forward(self, task: str):
model = next(iter(list_models(filter=task, sort="downloads", direction=-1)))
return model.id
```
Import the tool from `model_download.py` and use [`load_tool`] to load it into the agent.
```py
from model_download import HFModelDownloadsTool
from transformers import load_tool, CodeAgent
tool = HFModelDownloadsTool()
model_counter = load_tool(tool)
agent = CodeAgent(tools=[model_counter], add_base_tools=True)
```
Also consider sharing your tool to the Hub with [`~Tool.push_to_hub`] so that everyone can use it!
```py
from model_download import HFModelDownloadsTool
from transformers import load_tool, CodeAgent
tool = HFModelDownloadsTool()
tool.push_to_hub("{your_username}/hf-model-downloads")
model_counter = load_tool("m-ric/hf-model-downloads")
agent = CodeAgent(tools=[model_counter], add_base_tools=True)
```
## Add and replace tools
Once an agent is initialized, add or replace its available tools without reinitializing the agent from scratch.
Use [`add_tool`] to add a tool to an existing agent.
```py
from transformers import CodeAgent
agent = CodeAgent(tools=[], add_base_tools=True)
agent.toolbox.add_tool(model_download_counter)
```
Now you can use the default text-to-speech tool to read aloud the most downloaded model for the text-to-video task.
```py
agent.run(
"Can you read out loud the name of the model that has the most downloads on the 'text-to-video' task on the Hugging Face Hub and return the audio?"
)
```
> [!WARNING]
> When adding tools to an agent that already works well, it can bias the agent towards your tool or a tool other than the one currently defined.
Use [`update_tool`] to replace an agents existing tool. This is useful if the new tool is a one-to-one replacement of the existing tool because the agent already knows how to perform the task. The new tool should follow the same API as the tool it replaced or the system prompt template should be adapted to ensure all examples using the replaced tool are updated.
```py
agent.toolbox.update_tool(new_model_download_counter)
```
## ToolCollection
A [`ToolCollection`] is a collection of Hugging Face [Spaces](https://hf.co/spaces) that can be quickly loaded and used by an agent.
> [!TIP]
> Learn more about creating collections on the Hub.
Create a [`ToolCollection`] object and specify the `collection_slug` of the collection you want to use, and then pass it to the agent. To speed up the starting process, tools are only loaded if they're called by the agent.
The example loads a collection of image generation tools.
```py
from transformers import ToolCollection, ReactCodeAgent
image_tool_collection = ToolCollection(collection_slug="")
agent = ReactCodeAgent(tools=[*image_tool_collection], add_base_tools=True)
agent.run(
"Please draw me a picture of rivers and lakes."
)
```
## Tool integrations
Transformers supports tools from several other libraries, such as [gradio-tools](https://github.com/freddyaboulton/gradio-tools) and [LangChain](https://python.langchain.com/docs/introduction/).
### gradio-tools
gradio-tools is a library that enables [Gradio](https://www.gradio.app/) apps to be used as tools. With the wide variety of Gradio apps available, you can enhance your agent with a range of tools like generating images and videos or transcribing audio and summarizing it.
Import and instantiate a tool from gradio-tools, for example, the [StableDiffusionPromptGeneratorTool](https://github.com/freddyaboulton/gradio-tools/blob/main/gradio_tools/tools/prompt_generator.py). This tool can help improve prompts to generate better images.
> [!WARNING]
> gradio-tools require text inputs and outputs even when working with different modalities like images and audio, which are currently incompatible.
Use [`~Tool.from_gradio`] to load the prompt generator tool.
```py
from gradio_tools import StableDiffusionPromptGeneratorTool
from transformers import Tool, load_tool, CodeAgent
gradio_prompt_generator_tool = StableDiffusionPromptGeneratorTool()
prompt_generator_tool = Tool.from_gradio(gradio_prompt_generator_tool)
```
Now pass it to the agent along with a text-to-image tool.
```py
image_generation_tool = load_tool("huggingface-tools/text-to-image")
agent = CodeAgent(tools=[prompt_generator_tool, image_generation_tool], llm_engine=llm_engine)
agent.run(
"Improve this prompt, then generate an image of it.", prompt="A rabbit wearing a space suit"
)
```
### LangChain
LangChain is a library for working with LLMs which includes agents and tools. Use the [`~Tool.from_langchain`] method to load any LangChain tool into an agent.
The example below demonstrates how to use LangChains web search tool.
```py
from langchain.agents import load_tools
from transformers import Tool, ReactCodeAgent
search_tool = Tool.from_langchain(load_tools(["serpapi"])[0])
agent = ReactCodeAgent(tools=[search_tool])
agent.run("How many more blocks (also denoted as layers) in BERT base encoder than the encoder from the architecture proposed in Attention is All You Need?")
```
> Agents and tools were spun out into the standalone [smolagents](https://huggingface.co/docs/smolagents/index) library. They were removed from `transformers` in v4.52.