MCP 101: Build Your First MCP Server and Connect Claude to Any API (Step-by-Step)

What You'll Learn

By the end of this course, you will:

• Understand what MCP is and why it exists — the "USB-C for AI tools" standard
• Know the 3 component types — Tools, Resources, and Prompts — and when to use each
• Build a working MCP server from scratch in Python (~60 lines)
• Connect it to Claude Desktop and Cursor — see your tool called live
• Use Claude Code to generate MCP servers — 10-minute workflow for any integration
• Know which community servers to install for instant productivity

Prerequisites: Basic Python. pip install mcp requests. A Claude Desktop or Cursor installation to test with.

Time: ~20 minutes to read, ~45 minutes if you build and connect the weather server.

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The Problem MCP Solves

Every AI tool used to solve the integration problem differently. Claude had one plugin format. ChatGPT had another. Cursor had its own. If you wanted your database connected to multiple AI tools, you had to build the same integration three times.

MCP (Model Context Protocol) is Anthropic's answer to this: a single open standard that any AI client can speak, and any server can implement. Build once, connect everywhere.

Think of it like USB-C for AI tools. One standard connector, infinite devices.

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What MCP Actually Is

MCP is a protocol — a defined way for an AI client (like Claude Desktop, Cursor, or your own agent) to communicate with an MCP server (a process that exposes tools, data, or prompts).

The architecture is simple:

• MCP Client: The AI application (Claude Desktop, Cursor, your agent)
• MCP Server: A lightweight process you write that exposes capabilities
• Transport: How they communicate (stdio for local servers, HTTP/SSE for remote)

When the AI needs to call a tool — search the web, query a database, read a file — it sends a JSON-RPC message to the MCP server. The server executes the action and returns the result. The AI sees the result and continues reasoning.

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The 3 MCP Component Types

Every MCP server exposes its capabilities through three primitive types:

1. Tools

Functions the AI can call. This is the most common type.

Examples:

• search_web(query: str) — run a web search
• query_database(sql: str) — execute a SQL query
• send_email(to: str, subject: str, body: str) — send an email

Tools are the core of most MCP servers. They're what the AI actually does.

2. Resources

Data the AI can read. Think of these as virtual files.

Examples:

• file://documents/report.pdf — a document in your filesystem
• db://customers/recent — a dynamic view of database records
• api://github/issues — live issue list from GitHub

Resources are read-only. The AI can fetch them and use them as context.

3. Prompts

Reusable prompt templates the AI can invoke by name.

Examples:

• code-review-template — a structured prompt for reviewing PRs
• bug-report-format — a template for filing bug reports

Prompts let you standardize how the AI approaches common tasks.

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Build a Weather MCP Server in Python

Let's build a real MCP server. This one exposes a get_weather tool that fetches current conditions for any city.

Step 1: Install dependencies

pip install mcp requests

Step 2: Write the server

# weather_server.py
import asyncio
import json
import requests
from mcp.server import Server
from mcp.server.stdio import stdio_server
from mcp import types

app = Server("weather-server")

@app.list_tools()
async def list_tools() -> list[types.Tool]:
    return [
        types.Tool(
            name="get_weather",
            description="Get current weather conditions for a city",
            inputSchema={
                "type": "object",
                "properties": {
                    "city": {
                        "type": "string",
                        "description": "City name (e.g. 'London', 'New York')"
                    }
                },
                "required": ["city"]
            }
        )
    ]

@app.call_tool()
async def call_tool(name: str, arguments: dict) -> list[types.TextContent]:
    if name == "get_weather":
        city = arguments["city"]

        # Using wttr.in — free, no API key required
        response = requests.get(
            f"https://wttr.in/{city}?format=j1",
            timeout=10
        )
        response.raise_for_status()
        data = response.json()

        current = data["current_condition"][0]
        weather_summary = {
            "city": city,
            "temp_c": current["temp_C"],
            "temp_f": current["temp_F"],
            "description": current["weatherDesc"][0]["value"],
            "humidity": current["humidity"],
            "wind_kmph": current["windspeedKmph"]
        }

        return [types.TextContent(
            type="text",
            text=json.dumps(weather_summary, indent=2)
        )]

    raise ValueError(f"Unknown tool: {name}")

async def main():
    async with stdio_server() as (read_stream, write_stream):
        await app.run(
            read_stream,
            write_stream,
            app.create_initialization_options()
        )

if __name__ == "__main__":
    asyncio.run(main())

That's a complete MCP server. 60 lines of Python.

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Connect It to Claude Desktop

Find or create your Claude Desktop config file:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

Add your server:

{
  "mcpServers": {
    "weather": {
      "command": "python",
      "args": ["/absolute/path/to/weather_server.py"]
    }
  }
}

Restart Claude Desktop. You'll see a hammer icon in the chat interface — that means MCP tools are available. Ask Claude: "What's the weather in Tokyo?" and it will call your server automatically.

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Connect It to Cursor

In Cursor, go to Settings → MCP and add a new server entry:

{
  "weather": {
    "command": "python",
    "args": ["/absolute/path/to/weather_server.py"]
  }
}

Cursor will now be able to call your weather tool in the Composer and chat interfaces.

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Use Claude Code to Write MCP Servers

Here's a workflow that saves hours: use Claude Code to write your MCP servers for you.

Open your terminal and run:

claude

Then describe what you want:

"Write a Python MCP server that exposes a tool to query a SQLite database. The tool should take a SQL query string and return results as JSON. Use the mcp pip package with Server, list_tools, and call_tool. Add proper error handling for SQL errors."

Claude Code will generate the full server, including imports, error handling, and the stdio transport boilerplate. Review it, run it, iterate. This cuts initial MCP server development from an hour to under 10 minutes.

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Community MCP Servers Worth Installing

You don't have to build everything yourself. The official MCP servers repository has production-ready servers for the most common integrations:

github.com/modelcontextprotocol/servers

Highlights:

• Filesystem — Read/write local files with configurable allowed directories
• GitHub — Create issues, open PRs, search code, manage repositories
• Postgres — Run SQL queries against your database with schema inspection
• Brave Search — Web and local search via Brave's API (free tier available)
• Slack — Read channels, post messages, search history
• Google Maps — Geocoding, directions, place search

Each one ships with an install command and config snippet you can drop straight into Claude Desktop or Cursor.

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What You Can Build With MCP

A few directions worth exploring:

• Personal knowledge base: MCP server over your Obsidian vault or Notion workspace — Claude can search and reference your notes in any conversation
• Dev environment agent: Filesystem + GitHub + terminal MCP servers wired together so Claude can read your codebase, run tests, and open PRs
• Data analysis assistant: Postgres/SQLite MCP server so Claude can query your product database directly, no BI tool required
• Customer support agent: CRM + ticketing system MCP server so Claude can look up account history and create tickets mid-conversation

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Try These Now (3 Exercises)

Exercise 1 — Build the Weather Server (20 min): Copy the code above, save it as weather_server.py, install dependencies, and connect it to Claude Desktop or Cursor. Ask the AI "What's the weather in Tokyo?" and verify it calls your server. Bonus: add a get_forecast tool that returns the 3-day forecast from the same API.

Exercise 2 — Build a Custom Tool (30 min): Think of one thing you do repeatedly — look up a Jira ticket, query a database, check a service's status. Build an MCP server that exposes it as a tool. Use the weather server as your template. You'll be surprised how fast it goes once you have the boilerplate.

Exercise 3 — Use Claude Code to Generate One (10 min): Open Claude Code in your terminal and describe an MCP server you want: "Write a Python MCP server that exposes a tool to search my local Markdown files by keyword." Review what it generates. Compare the structure to the weather server. This teaches you the generation workflow for rapid MCP development.

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Key Takeaways

• MCP is a protocol, not a framework — JSON-RPC messages between a client (Claude, Cursor) and a server (your code)
• Tools, Resources, Prompts are the three primitives — Tools are the most common (functions the AI can call)
• A working MCP server is ~60 lines of Python — the barrier is low
• stdio transport for local servers, HTTP/SSE for remote — start with stdio
• Community servers exist for most common integrations — GitHub, Postgres, Filesystem, Slack
• Claude Code can generate MCP servers for you — describe what you want, review, ship

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What's Next

You now know what MCP is, how it works, and how to build and connect your first server. The next step is connecting multiple servers together and building agents that use several tools in a single reasoning chain.

Recommended next courses:

• AI Agents 101 — Part 1: What Is an AI Agent? — build the agent loop that calls tools like MCP servers
• AI Agents 101 — Part 2: Give Your Agent Real Tools — add web search, code execution, and error recovery
• 5 Levels of Coding Agents — see how MCP fits into progressively autonomous systems

If you want to go further — with hands-on sessions, working code, and a community of builders:

👉 Join AI Builder Club