Build MCP Servers

MCP is a protocol for building servers that can be used to build AI agents. In this guide, you’ll learn how to build MCP servers using Arcade.

Overview

In this guide, you’ll learn how to build MCP servers using arcade-mcp.

The main purpose of an MCP server is to provide tools to other applications. Let’s create a simple toolkit that returns up to date information about the user.

Setup your environment

This guide assumes you have uv installed. Let’s create a new project and install the necessary dependencies:

uv init
source .venv/bin/activate
uv pip install arcade-mcp

Create an MCP app

An MCP app is the main entry point for your MCP server. It contains the tools you want to expose, as well as the configuration for the server. Let’s create a simple MCP app that contains utility tools.

from arcade_mcp import MCPApp
 
app = MCPApp(
    name="my_server",
    version="1.0.0",
    title="My MCP Server",
    instructions="This server provides utility tools",
    log_level="INFO"
)

Add tools to the app

You can use the @app.tool decorator to add tools to the app. It’s recommended to annotate the parameters and return type of the tool.

from typing import Annotated
from datetime import datetime
 
@app.tool
def get_current_date_and_time() -> Annotated[str, "The current date and time"]:
    """Get the current date and time"""
    return datetime.now().strftime('%Y-%m-%d %H:%M:%S')
 
 
@app.tool
def calculate_average(
    numbers: Annotated[list[float], "The numbers to calculate the average of"],
) -> Annotated[float, "The average of the numbers"]:
    """Calculate the average of a list of numbers"""
    if not numbers:
        return 0.0
    return sum(numbers) / len(numbers)

Adding context to the tools

From the tools you can access a Context object that gives you several runtime features:

Logging
Secrets management
User Context
Progress Reporting

You can also decorate the tool with the secrets it requires to run, which must be present in the Context object.

@app.tool(requires_secrets=["DATABASE_CONNECTION_STRING"])
def get_current_date_and_time(context: Context) -> Annotated[str, "The current date and time"]:
    """Get the current date and time"""
    return datetime.now().strftime('%Y-%m-%d %H:%M:%S')

Guides Implement an MCP Client