An Interactive Tutorial
AI Nexus
A hands-on introduction to large language models, retrieval and AI agents: learn how modern AI actually works by using it yourself, no experience required.
Table of Contents
Introduction: Why This Guide Exists/introduction- Chapter 1Tokenization and the Cost of a Request/tokenizer
The exact token count Claude actually bills for, and what that costs to call.
- Chapter 2Large Language Models/chat
How a model turns a prompt into a reply, one token at a time.
- Chapter 3Retrieval-Augmented Generation/rag
Teaching an AI to look things up before it answers.
- Chapter 4AI Agents and Tool Use/agent
Watching an AI decide, act and use outside tools on its own.
- Chapter 5Automatic Text Summarization/summarize
Ranking a document's own sentences to condense it, without inventing a word.
- Chapter 6Semantic Caching/cache
Skipping a model call entirely when a new question means the same thing as an old one.
- Chapter 7Evaluating AI Outputs/eval
Scoring an answer against a reference instead of just eyeballing it.
- Chapter 8These Concepts in the Real World/enterprise
Real companies, real numbers: how this stuff is actually used at scale.
- Chapter 9The System Behind This Tutorial/architecture
A behind-the-scenes tour of the system running these chapters.
- Chapter 10How This Tutorial Was Built/building
The story of how an AI coding assistant and a person built this, together.