Tracing a Request End to End
Follow one tool call from prompt to result and back.
Tracing a Request End to End is a free MCP Academy lesson on CoddyKit — lesson 4 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.
Following One Tool Call
Let us trace a single tool call from start to finish. Watching the flow across host, client, and server ties all three roles together.
Step 1: You Ask
It begins with your prompt in the host, like asking for the weather. The host passes your words and the available tools to the model.
Step 2: The Model Decides
The model reads the request and picks a tool that fits. It does not run anything itself; it just chooses get_weather and the arguments.
Step 3: The Host Routes It
The host takes that choice and finds the matching server. It hands the call to the correct client, the one linked to that server.
Step 4: The Client Sends a Request
The client wraps it as a tools/call message and sends it down its connection to the server.
{ "method": "tools/call",
"params": { "name": "get_weather", "arguments": { "city": "Rome" } } }Step 5: The Server Does the Work
The server receives the call and runs the real function. It might hit an API or a database, then builds a result to return.
Step 6: The Result Travels Back
The server replies to the client with the answer. That response carries the same id as the request so the client knows what it matches.
Step 7: The Model Sees It
The client passes the result up to the host, which feeds it back to the model as new context for the conversation.
Step 8: You Get an Answer
Finally the model turns that data into a friendly reply, and the host shows it to you. The full round trip is complete.
Consent Can Pause the Flow
Before step five, the host may stop and ask for your approval. Tools only run once you allow them, keeping you in control.
The Whole Loop in One Line
Host to model to client to server, then all the way back. That single loop is the heart of every MCP interaction.
Quick Check
Recall which component actually executes the tool.
Recap
You traced a call end to end: you ask, the model picks, the client sends, the server runs it, and the result flows back to you. Fantastic work!
Frequently asked questions
Is the “Tracing a Request End to End” lesson free?
Yes — the full text of “Tracing a Request End to End” 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 “Tracing a Request End to End”?
Follow one tool call from prompt to result and back. 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 4 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Tracing a Request End to End” 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
- The Host: Claude Desktop & IDEs
- The Client: One Link Per Server
- The Server: Where Tools Live
- Tracing a Request End to End