LangGraph

The base URL goes on the model, not the agent. ChatOpenAI takes base_url; hand the instance to create_agent.

The base URL goes on the model object, not on the agent. ChatOpenAI takes base_url (alias openai_api_base), and create_agent accepts an initialized model instance — which is the path that carries a custom base URL, since the "provider:model" string form cannot.

pip install langchain-openai langgraph

from langchain_openai import ChatOpenAI
from langchain.agents import create_agent

model = ChatOpenAI(
    model="zen5",
    base_url="https://api.hanzo.ai/v1",
    api_key="sk-...",
)

agent = create_agent(model=model, tools=[])
result = agent.invoke({"messages": [{"role": "user", "content": "Hello"}]})

Lands on POST /v1/chat/completions.

Resolution order for the address, first match winning: the explicit base_url or openai_api_base argument, then OPENAI_API_BASE which LangChain reads at init, then OPENAI_BASE_URL which the underlying openai client reads. Setting the argument makes the other two irrelevant, which is why the snippet sets it.

MCP

langchain-mcp-adapters holds the client. The URL is the url key of a per-server entry.

pip install langchain-mcp-adapters

from langchain_mcp_adapters.client import MultiServerMCPClient

client = MultiServerMCPClient({
    "hanzo": {
        "transport": "http",
        "url": "https://api.hanzo.ai/v1/mcp",
        "headers": {"Authorization": "Bearer sk-..."},
    }
})

tools = await client.get_tools()
agent = create_agent(model=model, tools=tools)

MCP

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