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Agent Registry – LangChain / LangGraph

Integrate a LumoAuth-registered agent with LangChain and LangGraph to authenticate, enforce budget policies, and perform token exchange for secured MCP servers.

Prerequisites

Install the lumoauth package and set the environment variables LUMOAUTH_URL, LUMOAUTH_TENANT, AGENT_CLIENT_ID, and AGENT_CLIENT_SECRET. See Install the SDK.

Install​

pip install lumoauth langchain-openai langgraph

Example​

from langchain_openai import ChatOpenAI
from langchain_core.tools import tool
from langgraph.prebuilt import create_react_agent
from lumoauth import LumoAuthAgent

# 1. Initialize and authenticate the LumoAuth Agent
lumo_agent = LumoAuthAgent()
lumo_agent.authenticate()

# 2. Define tools that check LumoAuth capabilities
@tool
def search_company_documents(query: str) -> str:
    """Search internal company documents."""
    if not lumo_agent.has_capability('read:documents'):
        return "Error: Agent lacks 'read:documents' capability."
    return f"Found 3 documents matching '{query}'"

@tool
def query_financial_mcp(metric: str) -> str:
    """Query the secured financial metrics MCP server."""
    if not lumo_agent.has_capability('mcp:financial'):
        return "Error: Agent lacks 'mcp:financial' capability."
    mcp_token = lumo_agent.get_mcp_token("urn:mcp:financial-data")
    if not mcp_token:
        return "Error: Failed to obtain token for Financial MCP server."
    return f"Retrieved {metric}: $1.2M (Authenticated via MCP Token Exchange)"

# 3. Create the LangGraph ReAct Agent
tools = [search_company_documents, query_financial_mcp]
llm = ChatOpenAI(model="gpt-4", temperature=0)
agent_executor = create_react_agent(llm, tools)

# 4. Run the graph
def run_agent_workflow(user_query: str):
    if lumo_agent.is_budget_exhausted():
        print("Agent budget exhausted for today.")
        return

    events = agent_executor.stream(
        {"messages": [("user", user_query)]},
        stream_mode="values",
    )
    for event in events:
        event["messages"][-1].pretty_print()

if __name__ == "__main__":
    run_agent_workflow("Search documents for Q3 performance, then query the financial MCP for EBITDA.")

How It Works​

StepWhat happens
LumoAuthAgent()Reads credentials from env vars and initialises the client
lumo_agent.authenticate()Performs OAuth 2.0 client-credentials flow
has_capability(...)Guards tool execution with LumoAuth capability checks
get_mcp_token(...)Exchanges the agent token for an MCP-specific token (RFC 8693)
is_budget_exhausted()Prevents the LangGraph run if the agent's daily budget is used up

Next Steps​