MCP vs Function Calling
How MCP differs from raw model tool calls.
MCP vs Function Calling is a free MCP Academy lesson on CoddyKit — lesson 1 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the MCP Academy learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Two Ways to Give Models Tools
You already know models can call tools. So where does MCP fit? It is a standard way to ship those tools, not a replacement for the idea.
What Function Calling Is
With function calling, you define each tool inline in your own API request to the model, and your code runs whatever the model picks.
tools = [{
"name": "get_weather",
"input_schema": {"type": "object"}
}]Tools Live in Your App
In plain function calling, the tool list and the code that runs them both live inside your one app. Nothing is shared with anyone else.
MCP Moves Tools Out
MCP takes those tools and puts them behind a separate server. Any MCP-aware app can connect and use them without copying your code.
Reusable Across Apps
The big win is reuse: write a tool once as an MCP server, and Claude Desktop, an IDE, or your own agent can all share it.
Function Calling Is Per-Request
Function calling ships the tool schemas in every request. It is simple and direct, but each app must carry its own copy of every tool.
MCP Is Discoverable
An MCP client asks the server what it offers at connect time. Tools are discovered live, not hardcoded into each request.
tools = await session.list_tools()They Work Together
These are not rivals. Under the hood an MCP host often turns server tools into ordinary function-calling tools for the model to pick.
When Function Calling Wins
For a single app with a few private tools, plain function calling is lighter. No extra server, no transport, just your code.
When MCP Wins
Reach for MCP when the same capability must serve many clients, or when users plug your tools into apps you do not control.
The Mental Model
Think of function calling as a tool you carry in your pocket, and MCP as that tool published in a shop where anyone can pick it up.
Quick Check
Pick the clearest difference between MCP and plain function calling.
Recap
Function calling defines tools inline in one app; MCP publishes them as a reusable server. Same core idea, wider reach. Nice work! 🎉
Frequently asked questions
Is the “MCP vs Function Calling” lesson free?
Yes — the full text of “MCP vs Function Calling” is free to read here on the web, and the MCP Academy course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the MCP Academy course, upgrade to CoddyKit PRO.
What will I learn in “MCP vs Function Calling”?
How MCP differs from raw model tool calls. You practise MCP Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start MCP Academy?
No prior experience is required. MCP Academy on CoddyKit is structured for beginners through advanced learners; this is — lesson 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “MCP vs Function Calling” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this MCP Academy lesson?
Yes. Every MCP Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- MCP vs Function Calling
- MCP Inside Agent Frameworks
- Agent-to-Agent with A2A
- Where MCP Is Heading Next