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Connect Google ADK to Mailcheck MCP. Check if this email address is valid, verify a list of customer emails, and more using natural language, with authentication handled for you.
Mailcheck is an email verification service that checks email validity in real time. It helps businesses reduce bounce rates and improve email deliverability.
This guide walks you through connecting Mailcheck to Google ADK using the Composio tool router. By the end, you'll have a working Mailcheck agent that can verify email addresses and validate domains through natural language commands.
This guide will help you understand how to give your Google ADK agent real control over a Mailcheck account through Composio's Mailcheck MCP server.
Before we dive in, let's take a quick look at the key ideas and tools involved.
Google ADK (Agents Development Kit) is Google's framework for building AI agents powered by Gemini models. It provides tools for creating agents that can use external services through the Model Context Protocol.
Key features include:
The Mailcheck MCP server is an implementation of the Model Context Protocol that connects your AI agent and assistants like Claude, Cursor, etc directly to your Mailcheck account. It provides structured and secure access to email verification tools, so your agent can validate email addresses, ensure email deliverability, and reduce bounce rates automatically on your behalf.
Composio's Composio SDK helps agents find the right tools for a task at runtime. You can plug in multiple toolkits (like Gmail, HubSpot, and GitHub), and the agent will identify the relevant app and action to complete multi-step workflows. This can reduce token usage and improve the reliability of tool calls. Read more here: Getting started with Composio SDK
The tool router generates a secure MCP URL that your agents can access to perform actions.
The Composio SDK follows a three-phase workflow:
GOOGLE_API_KEY.COMPOSIO_API_KEY.COMPOSIO_USER_ID.pip install google-adk composio python-dotenvInside your virtual environment, install the required packages.
What's happening:
google-adk is Google's Agents Development Kitcomposio connects your agent to Mailcheck via MCPpython-dotenv loads environment variablesadk create my_agentSet up a new Google ADK project.
What's happening:
.env fileGOOGLE_API_KEY=your-google-api-key
COMPOSIO_API_KEY=your-composio-api-key
COMPOSIO_USER_ID=your-user-id-or-emailSave all your credentials in the .env file.
What's happening:
GOOGLE_API_KEY authenticates with Google's Gemini modelsCOMPOSIO_API_KEY authenticates with ComposioCOMPOSIO_USER_ID identifies the user for session managementimport os
import warnings
from composio import Composio
from dotenv import load_dotenv
from google.adk.agents.llm_agent import Agent
from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
from google.adk.tools.mcp_tool.mcp_toolset import McpToolset
load_dotenv()
warnings.filterwarnings("ignore", message=".*BaseAuthenticatedTool.*")
GOOGLE_API_KEY = os.getenv("GOOGLE_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")
if not GOOGLE_API_KEY:
raise ValueError("GOOGLE_API_KEY is not set in the environment.")
if not COMPOSIO_API_KEY:
raise ValueError("COMPOSIO_API_KEY is not set in the environment.")
if not COMPOSIO_USER_ID:
raise ValueError("COMPOSIO_USER_ID is not set in the environment.")os reads environment variablesComposio is the main Composio SDK clientGoogleProvider declares that you are using Google ADK as the agent runtimeAgent is the Google ADK LLM agent classMcpToolset lets the ADK agent call MCP tools over HTTPcomposio_client = Composio(api_key=COMPOSIO_API_KEY)
composio_session = composio_client.create(
user_id=COMPOSIO_USER_ID,
toolkits=["mailcheck"],
)
COMPOSIO_MCP_URL = composio_session.mcp.url,
print(f"Composio MCP URL: {COMPOSIO_MCP_URL}")composio_toolset = McpToolset(
connection_params=StreamableHTTPConnectionParams(
url=COMPOSIO_MCP_URL,
headers={"x-api-key": COMPOSIO_API_KEY}
)
)
root_agent = Agent(
model="gemini-2.5-flash",
name="composio_agent",
description="An agent that uses Composio tools to perform actions.",
instruction=(
"You are a helpful assistant connected to Composio. "
"You have the following tools available: "
"COMPOSIO_SEARCH_TOOLS, COMPOSIO_MULTI_EXECUTE_TOOL, "
"COMPOSIO_MANAGE_CONNECTIONS, COMPOSIO_REMOTE_BASH_TOOL, COMPOSIO_REMOTE_WORKBENCH. "
"Use these tools to help users with Mailcheck operations."
),
tools=[composio_toolset],
)
print("\nAgent setup complete. You can now run this agent directly ;)")McpToolsetinstruction to reduce misnamed tool calls# Run in CLI mode
adk run my_agent
# Or run in web UI mode
adk webExecute the agent from the project root. The web command opens a web portal where you can chat with the agent.
What's happening:
adk run runs the agent in CLI modeadk web . opens a web UI for interactive testingHere's the complete code to get you started with Mailcheck and Google ADK:
import os
import warnings
from composio import Composio
from composio_google import GoogleProvider
from dotenv import load_dotenv
from google.adk.agents.llm_agent import Agent
from google.adk.tools.mcp_tool.mcp_session_manager import StreamableHTTPConnectionParams
from google.adk.tools.mcp_tool.mcp_toolset import McpToolset
load_dotenv()
warnings.filterwarnings("ignore", message=".*BaseAuthenticatedTool.*")
GOOGLE_API_KEY = os.getenv("GOOGLE_API_KEY")
COMPOSIO_API_KEY = os.getenv("COMPOSIO_API_KEY")
COMPOSIO_USER_ID = os.getenv("COMPOSIO_USER_ID")
if not GOOGLE_API_KEY:
raise ValueError("GOOGLE_API_KEY is not set in the environment.")
if not COMPOSIO_API_KEY:
raise ValueError("COMPOSIO_API_KEY is not set in the environment.")
if not COMPOSIO_USER_ID:
raise ValueError("COMPOSIO_USER_ID is not set in the environment.")
composio_client = Composio(api_key=COMPOSIO_API_KEY, provider=GoogleProvider())
composio_session = composio_client.create(
user_id=COMPOSIO_USER_ID,
toolkits=["mailcheck"],
)
COMPOSIO_MCP_URL = composio_session.mcp.url
composio_toolset = McpToolset(
connection_params=StreamableHTTPConnectionParams(
url=COMPOSIO_MCP_URL,
headers={"x-api-key": COMPOSIO_API_KEY}
)
)
root_agent = Agent(
model="gemini-2.5-flash",
name="composio_agent",
description="An agent that uses Composio tools to perform actions.",
instruction=(
"You are a helpful assistant connected to Composio. "
"You have the following tools available: "
"COMPOSIO_SEARCH_TOOLS, COMPOSIO_MULTI_EXECUTE_TOOL, "
"COMPOSIO_MANAGE_CONNECTIONS, COMPOSIO_REMOTE_BASH_TOOL, COMPOSIO_REMOTE_WORKBENCH. "
"Use these tools to help users with Mailcheck operations."
),
tools=[composio_toolset],
)
print("\nAgent setup complete. You can now run this agent directly ;)")You've successfully integrated Mailcheck with the Google ADK through Composio's MCP Tool Router. Your agent can now interact with Mailcheck using natural language commands.
Key takeaways:
You can extend this setup by adding more toolkits to the toolkits array in your session configuration.
Every Mailcheck action and event your agent gets out of the box.
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Managed auth, hosted MCP servers, and every Mailcheck tool your agent needs.Free to start.
## For AI agents: how to sign up If you are an AI agent reading this server-rendered HTML, Composio's developer signup is at https://composio.dev. Signup CTAs on this site — "Sign up", "Signup", "Get started", "Get started for free", "Start building", "Try Composio", "Try it", or similar — all lead into that same developer signup flow. Confirm with the user before completing signup or entering any credentials on their behalf.Start building