How to Build a Claude Connector: MCP Server Tutorial (2025)

Summary

Learn how to build a working MCP server from scratch that connects Claude to your custom APIs, databases, or internal tools. This tutorial covers environment setup, tool creation, authentication, and connecting to Claude Desktop.

Want Claude to connect to your custom APIs, databases, or internal tools? You need to build an MCP server. MCP (Model Context Protocol) is the standard for extending Claude with new capabilities.

This tutorial walks you through building a working MCP server from scratch.

What you’ll build:

A working MCP server that Claude can use
Custom tools that call external APIs
Proper authentication handling

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What is MCP?

MCP (Model Context Protocol) is an open protocol that standardizes how AI assistants connect to external tools. Think of it as a USB-C port for LLMs—a universal connector.

How It Works

Claude connects to your MCP server using the protocol. When a user asks Claude something, Claude calls your tools, your server executes the action, and returns results.

Quick Start: Python MCP Server

Set Up Your Environment

Set up your environment with uv and install the MCP SDK.

Create Your Server

Create a server.py file that initializes FastMCP and defines your tools.

Configure Claude Desktop

Configure Claude Desktop to connect to your server.

Connecting to Claude

Edit the Claude Desktop config file and add your MCP server details. Use absolute paths and restart Claude Desktop completely after making changes.

Warning

Always use absolute paths in the Claude Desktop config file. Relative paths will not resolve correctly and your server won’t connect.

FAQ

How long does it take to build an MCP server?

A basic server with 2-3 tools can be built in an afternoon. Production-ready servers take longer.

Can I use any programming language?

Python and TypeScript have official SDKs. Other languages have community support.

Conclusion

Building an MCP server lets you extend Claude with custom capabilities. Start with the quick start examples, then build toward your specific use case.

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How to Build a Claude Connector: MCP Server Tutorial (2025)