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How to build MCP Servers and Clients from Scratch

Developer Harsh on March 16, 2025

What is MCP Think of MCP as a USB C port on a laptop. With it, you can charge your laptop, perform data transfer, connect to other displ...

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Arun Yadav • Mar 25 • Edited

Open the terminal and navigate to your working environment.

Run the command:

pip install uv
mcp dev calculator.py

If prompted, install the CLI by pressing ‘y’ or do it manually, then rerun the command.

Some people might get stuck here, but don’t worry—I’m here to help! Just replace server.py with calculator.py, and you’re good to go. 🚀

Developer Harsh • Mar 25

Thanks for the addition, it will help many

Aliosh • Mar 25

"Traditional API" -> What would be a traditional API?

Are you referring to the HTTP protocol? MCP is a protocol and Http is another. An api can share the same interface, adaptable for any of these protocols. This is what I have done on my MCP server, with clean architecture: github.com/alioshr/memory-bank-mcp

Developer Harsh • Mar 27

Yes HTTP Protocols / Custom API we design for products.

I will check the repo. Thanks for sharing 🙏

Manuel Alzola Würth • Mar 23

Can FastMCP be used on a flask server?

wenxuwan • Mar 25

Same question.

Developer Harsh • Mar 25

Answered in previous comment

Developer Harsh • Mar 25

FastMCP isn’t designed to be used directly within a Flask server.

However you can run them as separate services and facilitate communication between them to achieve the desired integration.

wenxuwan • Mar 26

Thanks for your reply, now I converted the flask app to an asgi app via WsgiToAsgi and then mounted the asgi_flask app to the MCP's sse_app (s se_app is a Starlette app)

class SofaApp(FastMCP, Flask):
    def __init__(self):
        FastMCP.__init__(self, __name__)
        Flask.__init__(self, __name__)
        self.asgi_flask = WsgiToAsgi(self)
        self.sofa_app = self.sse_app()
        self.sofa_app.mount("/", self.asgi_flask)

Developer Harsh • Mar 29

Great

Developer Harsh • Mar 16 • Edited

Read the better formatted version at Composio Blogs- Harsh

artydev • Apr 2

Thank you very much, I will try it for sure :-)

John Charlie • Mar 26

Amazing article! But what about creating our own MCP Client?

Developer Harsh • Mar 27

For MCP client you can use Cursor, WindSurf, Warp, Composio. In case you want to create your own using mcp-client SDK. I will cover that in another blog:)