# LangChain Setup

> Connect LangChain agents to graph8 via MCP using langchain-mcp-adapters and LangGraph

Source: https://docs.graph8.com/developers/langchain-setup/

Connect a LangChain or LangGraph agent to graph8's MCP server. Two transports are supported: hosted (remote OAuth) and self-hosted (local stdio).

> **Tip:**
> Try the developer tier free - 1,000 credits, no card required. [Get started](https://auth.graph8.com/en/signup).

## Prerequisites

- Python 3.10+
- `langchain-mcp-adapters`, `langgraph`, `langchain-anthropic` (or your provider of choice)
- A graph8 account with a personal API key from **Profile -> Developer** (for stdio), or any active session (for OAuth)

```bash
pip install langchain-mcp-adapters langgraph langchain-anthropic
```

## Hosted MCP (remote OAuth)

Use this when you want graph8 to handle auth via OAuth and you do not want to install the MCP server locally. The agent connects to `https://be.graph8.com/mcp/` over Streamable HTTP and prompts you to sign in once.

```python
import asyncio
import os

from langchain_mcp_adapters.client import MultiServerMCPClient
from langgraph.prebuilt import create_react_agent
from langchain_anthropic import ChatAnthropic

async def main() -> None:
    client = MultiServerMCPClient(
        {
            "graph8": {
                "transport": "streamable_http",
                "url": "https://be.graph8.com/mcp/",
            }
        }
    )

    tools = await client.get_tools()
    model = ChatAnthropic(
        model="claude-sonnet-4",
        api_key=os.environ["ANTHROPIC_API_KEY"],
    )
    agent = create_react_agent(model, tools)

    result = await agent.ainvoke(
        {
            "messages": [
                (
                    "user",
                    "Find 25 VP Engineering at Series B SaaS companies "
                    "in the United States. Return name, company, and title.",
                )
            ]
        }
    )
    print(result["messages"][-1].content)

if __name__ == "__main__":
    asyncio.run(main())
```

The first run opens a browser window for OAuth. Subsequent runs reuse the token cached by the MCP client.

## Self-hosted MCP (stdio)

Use this when you cannot rely on browser-based OAuth (CI, headless servers, air-gapped dev). Requires `uv` or Python on the host and a personal API key.

```bash
export G8_API_KEY="g8_..."
```

```python
import asyncio
import os

from langchain_mcp_adapters.client import MultiServerMCPClient
from langgraph.prebuilt import create_react_agent
from langchain_anthropic import ChatAnthropic

async def main() -> None:
    client = MultiServerMCPClient(
        {
            "graph8": {
                "transport": "stdio",
                "command": "uvx",
                "args": ["g8-mcp-server"],
                "env": {
                    "G8_API_KEY": os.environ["G8_API_KEY"],
                    "G8_MCP_MODE": "gtm",
                },
            }
        }
    )

    tools = await client.get_tools()
    model = ChatAnthropic(model="claude-sonnet-4")
    agent = create_react_agent(model, tools)

    result = await agent.ainvoke(
        {"messages": [("user", "Search my CRM for contacts at Stripe.")]}
    )
    print(result["messages"][-1].content)

if __name__ == "__main__":
    asyncio.run(main())
```

Set `G8_MCP_MODE` to `dev`, `gtm`, or `all` to scope the tool set. See [Modes](https://docs.graph8.com/developers/mcp/#modes).

## Worked example: prospect, qualify, enroll

End-to-end LangGraph agent that finds prospects, saves them to a list, and enrolls the list in a sequence. Confirm credit-charging steps before running.

```python
prompt = (
    "1. Use g8_find_contacts to preview 50 VP Engineering at Series B SaaS in the US.\n"
    "2. Show me the top 10 by company size and ask me to confirm.\n"
    "3. On confirmation, use g8_build_contact_list to save them to a new list "
    "named 'Series B SaaS VP Eng'.\n"
    "4. Then use g8_list_sequences to find a sequence named 'New SaaS Outreach'.\n"
    "5. Use g8_add_to_sequence to enroll the saved contacts. Ask me to confirm "
    "before enrolling."
)
```

graph8 enforces a confirmation rule for credit-charging tools (`g8_build_contact_list`, `g8_add_to_sequence`). The agent will pause and ask before any of these run.

## Related

- [MCP Server overview](https://docs.graph8.com/developers/mcp/)
- [MCP Tool Reference](https://docs.graph8.com/developers/mcp-tools/)
- [MCP FAQ](https://docs.graph8.com/developers/mcp-faq/)
- [End-to-end examples](https://docs.graph8.com/developers/mcp-examples/)