ADK and FastMCP Server example

This example demonstrates connecting to a remote FastMCP server that provides math operations(eg. addition).

Step 0: Deploy FastMCP Server to Cloud Run

Repo link: https://github.com/gitrey/fastmcp-demo

#server.py
from fastmcp import FastMCP
import asyncio

mcp = FastMCP("FastMCP Demo Server")

@mcp.tool()
def add(a: int, b: int) -> int:
    """Add two numbers"""
    return a + b

if __name__ == "__main__":
    asyncio.run(mcp.run_sse_async(host="0.0.0.0", port=8080))

Ensure your MCP server project has the following files in the root directory(eg. ./fastmcp-demo):

• server.py: Your main application code using FastMCP.

• requirements.txt: Lists the Python dependencies.

  fastmcp
  asyncio
  

• Procfile: Tells Cloud Run how to start your web server.

  web: python server.py
  

  (Note: This assumes your FastMCP instance is named mcp within your server.py file. Adjust server:mcp if your filename or instance name is different.)

Execute Cloud Run Deployment command from your FastMCP server directory(eg. ./fastmcp-demo):

    gcloud run deploy fastmcp-demo \
        --source . \
        --region YOUR_REGION

Agent config

Step 1: Attach the FastMCP Server to your ADK agent via MCPToolset

Create agent.py and use the following code snippet to define a function that initializes the MCPToolset.

• Important: Replace Cloud Run service url with the one you deployed in previous step.

# agent.py

import os

import google.auth
import google.oauth2.id_token
import google.auth.transport.requests

from contextlib import AsyncExitStack

from google.adk.agents import Agent
from google.adk.tools.tool_context import ToolContext
from google.adk.tools.mcp_tool.mcp_toolset import MCPToolset, SseServerParams

_, project_id = google.auth.default()
os.environ.setdefault("GOOGLE_CLOUD_PROJECT", project_id)
os.environ.setdefault("GOOGLE_CLOUD_LOCATION", "us-central1")
os.environ.setdefault("GOOGLE_GENAI_USE_VERTEXAI", "True")


async def get_sum(a: int, b: int) -> int:
    """Get sum for two numbers

    Args:
        a: number
        b: number

    Returns:
        the sum of two numbers.
    """
    common_exit_stack = AsyncExitStack()

    mcp_tool_url = "https://fastmcp-demo-00000000000.us-central1.run.app"
    request = google.auth.transport.requests.Request()
    target_audience = mcp_tool_url

    # For an agent running on GCP runtimes, consider using:
    # https://cloud.google.com/docs/authentication/get-id-token#metadata-server
    # This can be used at global scope of agent, and then use the .refresh() method
    # on the credential which will only call metadata service once per hour
    id_token = google.oauth2.id_token.fetch_id_token(request, target_audience)

    tools, _ = await MCPToolset.from_server(
        connection_params=SseServerParams(
            url="https://fastmcp-demo-00000000000.us-central1.run.app/sse",
            headers={"Authorization": f"Bearer {id_token}"},
        ),
        async_exit_stack=common_exit_stack
    )

    return await tools[0].run_async(
        args={
            "a": a,
            "b": b,
        },
        tool_context=None,
    )

root_agent = Agent(
    name="root_agent",
    model="gemini-2.0-flash",
    instruction="You are a helpful AI assistant designed to provide accurate and useful information.",
    tools=[get_sum],
)

Step 2: Create an init file

Create an __init__.py in the same folder as the agent.py above

# __init__.py
from . import agent

Step 3: Setup credentials to run agent locally

To run the agent locally, you need to set up your Google Cloud credentials. You can do this by setting the GOOGLE_APPLICATION_CREDENTIALS environment variable to point to your service account key file.

You can do this by running the following command in your terminal:

export GOOGLE_APPLICATION_CREDENTIALS=/path/to/service-account-key.json

Make sure to replace /path/to/service-account-key.json with the actual path to your service account key file.

Step 4: Run the agent

Run adk web from the repo root directory (ensure your virtual environment is active):

adk web

A successfully interaction will yield a response by accessing your remote FastMCP server, like below: