langchain-ai--langgraph/libs/prebuilt/README.md

# LangGraph Prebuilt

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To help you ship LangGraph apps to production faster, check out [LangSmith](https://www.langchain.com/langsmith).
[LangSmith](https://www.langchain.com/langsmith) is a unified developer platform for building, testing, and monitoring LLM applications.

## Quick Install

```bash
uv add langgraph
```

## 🤔 What is this?

This library defines high-level APIs for creating and executing LangGraph agents and tools. It includes prebuilt components such as `create_react_agent`, `ToolNode`, validation helpers, and Agent Inbox schemas.

## 📖 Documentation

For full documentation, see the [API reference](https://reference.langchain.com/python/langgraph.prebuilt/). For conceptual guides and tutorials, see the [LangGraph Docs](https://docs.langchain.com/oss/python/langgraph/overview).

> [!IMPORTANT]
> This library is bundled with `langgraph`; most users should install `langgraph` instead of installing `langgraph-prebuilt` directly.

## Agents

`langgraph-prebuilt` provides an [implementation](https://reference.langchain.com/python/langgraph.prebuilt/chat_agent_executor/create_react_agent) of a tool-calling ReAct-style agent - `create_react_agent`:

```bash
uv add langchain-anthropic
```

```python
from langchain_anthropic import ChatAnthropic
from langgraph.prebuilt import create_react_agent

# Define the tools for the agent to use
def search(query: str):
    """Call to surf the web."""
    # This is a placeholder, but don't tell the LLM that...
    if "sf" in query.lower() or "san francisco" in query.lower():
        return "It's 60 degrees and foggy."
    return "It's 90 degrees and sunny."

tools = [search]
model = ChatAnthropic(model="claude-3-7-sonnet-latest")

app = create_react_agent(model, tools)
# run the agent
app.invoke(
    {"messages": [{"role": "user", "content": "what is the weather in sf"}]},
)
```

## Tools

### ToolNode

`langgraph-prebuilt` provides an [implementation](https://reference.langchain.com/python/langgraph.prebuilt/tool_node/ToolNode) of a node that executes tool calls - `ToolNode`:

```python
from langgraph.prebuilt import ToolNode
from langchain_core.messages import AIMessage

def search(query: str):
    """Call to surf the web."""
    # This is a placeholder, but don't tell the LLM that...
    if "sf" in query.lower() or "san francisco" in query.lower():
        return "It's 60 degrees and foggy."
    return "It's 90 degrees and sunny."

tool_node = ToolNode([search])
tool_calls = [{"name": "search", "args": {"query": "what is the weather in sf"}, "id": "1"}]
ai_message = AIMessage(content="", tool_calls=tool_calls)
# execute tool call
tool_node.invoke({"messages": [ai_message]})
```

### ValidationNode

`langgraph-prebuilt` provides an [implementation](https://reference.langchain.com/python/langgraph.prebuilt/tool_validator/ValidationNode) of a node that validates tool calls against a pydantic schema - `ValidationNode`:

```python
from pydantic import BaseModel, field_validator
from langgraph.prebuilt import ValidationNode
from langchain_core.messages import AIMessage


class SelectNumber(BaseModel):
    a: int

    @field_validator("a")
    def a_must_be_meaningful(cls, v):
        if v != 37:
            raise ValueError("Only 37 is allowed")
        return v

validation_node = ValidationNode([SelectNumber])
validation_node.invoke({
    "messages": [AIMessage("", tool_calls=[{"name": "SelectNumber", "args": {"a": 42}, "id": "1"}])]
})
```

## Agent Inbox

The library contains schemas for using the [Agent Inbox](https://github.com/langchain-ai/agent-inbox) with LangGraph agents. Learn more about how to use Agent Inbox [here](https://github.com/langchain-ai/agent-inbox#interrupts).

```python
from langgraph.types import interrupt
from langgraph.prebuilt.interrupt import HumanInterrupt, HumanResponse

def my_graph_function():
    # Extract the last tool call from the `messages` field in the state
    tool_call = state["messages"][-1].tool_calls[0]
    # Create an interrupt
    request: HumanInterrupt = {
        "action_request": {
            "action": tool_call['name'],
            "args": tool_call['args']
        },
        "config": {
            "allow_ignore": True,
            "allow_respond": True,
            "allow_edit": False,
            "allow_accept": False
        },
        "description": _generate_email_markdown(state) # Generate a detailed markdown description.
    }
    # Send the interrupt request inside a list, and extract the first response
    response = interrupt([request])[0]
    if response['type'] == "response":
        # Do something with the response
    ...
```

## 📕 Releases & Versioning

See our [Releases](https://docs.langchain.com/oss/python/release-policy) and [Versioning](https://docs.langchain.com/oss/python/versioning) policies.

## 💁 Contributing

As an open-source project in a rapidly developing field, we are extremely open to contributions, whether it be in the form of a new feature, improved infrastructure, or better documentation.

For detailed information on how to contribute, see the [Contributing Guide](https://docs.langchain.com/oss/python/contributing/overview).