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Building an AI Agent from Scratch — RAG · Multi-Agent · MCP

Build an AI agent from scratch using Python and a single while loop, without any frameworks. In the introductory section, you’ll add tool design, failures and costs, memory, human approval, evaluation, and a web interface one by one to complete a small coding agent. In the hands-on section, you’ll implement RAG, multi-agent systems, and an MCP server yourself using real business reports from DART, then compare them numerically with LangChain and LangGraph.

8 learners are taking this course

Level Basic

Course period Unlimited

Python
Python
FastAPI
FastAPI
LLM
LLM
openAI API
openAI API
AI Agent
AI Agent
Python
Python
FastAPI
FastAPI
LLM
LLM
openAI API
openAI API
AI Agent
AI Agent

What you will gain after the course

  • Implement an agent loop that calls tools using only the OpenAI SDK and a while loop, without a framework.

  • Design tools that models use well: a tool registry, descriptions, and returning results concisely and structurally

  • How to prevent infinite loops, invalid JSON, and API errors with safeguards, and how to measure actual charges using usage.cost

  • Manage short-term and long-term memory using conversation history reduction, summarization, session storage, and note-taking tools.

  • A flow that shows the diff and obtains human approval before writing files or executing commands

  • Compare the models (DeepSeek and GLM) by measuring pass rate, average cost, and number of calls using an evaluation set.

  • A local web interface that displays real-time progress by episode using FastAPI and SSE

  • Complete a mini coding agent that reads failing tests, fixes them, and runs them again.

  • (Hands-On) Build RAG Directly with Actual Business Reports (DART) and Measure Accuracy Using BM25 · Hybrid Search · Reranking · Source Verification

  • (Hands-on) Build a multi-agent research team and citation verifier, port them to LangChain · LangGraph, and compare them quantitatively.

  • (Hands-on) Build an MCP server manually → with the official SDK → through remote deployment and token authentication, and cover security measures to block modified servers.

Recommended for
these people

Who is this course right for?

  • A developer who knows the basics of Python but has never built anything using an AI API.

  • People who have tried frameworks like LangChain and are curious about what actually happens inside them

  • For those who use coding agents like Claude Code and Codex and wonder, "How does this work?&quot

  • Those who want to build a small in-house automation agent themselves and control costs and failures on their own

  • Those who have completed the introduction and want to build RAG, multi-agent systems, and MCP using real data.

Need to know before starting?

  • Python Basics: Functions, dict/list, for/while, try/except, f-string (Part 0: We’ll review them again with refresher.py)

  • Using `cd`, Running Commands, and Handling Environment Variables (`.env`) in the Terminal

  • It’s enough to have simply heard of HTTP APIs or JSON. It’s okay if you’re new to AI APIs.

Hello
This is dante

Career Verified

136

Learners

17

Reviews

4.5

Rating

3

Courses

I’ll personally test and teach you how to assign tasks to AI.

Hello, I’m Dante. I previously worked as a developer at Naver and Coupang, and I currently work as a developer in Silicon Valley. Every day, I use AI coding tools such as Claude Code and Codex for real work, measuring what works and what doesn’t with data and incorporating those findings into my courses.

✔ Industry Developer — Former developer at Naver and Coupang, currently a Silicon Valley developer
✔ Author — 『The Complete Guide to Vibe Coding with Codex』, 『Relearning React in Depth: Inside React』
✔ Mentor — Over 400 mentoring sessions (practical AI agent implementation, frontend development and learning consulting)
✔ YouTube “Dante” — A channel that directly tests and compares new AI coding tools

This is how I create my courses
1. I don’t just explain things verbally — I show the input → execution → result exactly as they appear on the actual screen.
2. I measure it myself — Instead of saying “this is better,” I measure and show the time, token usage, and number of bugs. Even results that are unfavorable are shown as they are.
3. I finish with visible results — I create deliverables that work all the way through using real public data.
4. I make all the code public — The practice files and solutions are available in a public GitHub repository.

Courses · Mentoring
· Claude Code in Practice — From Installation to Harnesses — https://inf.run/yKj3F
· An Introduction to Dante’s Complete Codex Guide — https://inf.run/dzVtP
· Building an AI Agent from Scratch — RAG · Multi-Agent Systems · MCP — https://inf.run/jY8Bz
· 1:1 Mentoring — https://mentoring.inflearn.com/mentors/1535

Books
“The Complete Guide to Vibe Coding Codex Today” Kyobo Bookstore · YES24 · Aladin
“Inside React: Learning It in Depth Again” Kyobo Bookstore · YES24 · Aladin

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Curriculum

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49 lectures ∙ (5hr 16min)

Course Materials:

Lecture resources
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