Free book · 19 chapters · v3
Context Engineering 101 is the practical guide to building AI agents that stay sharp at step twenty — by designing what the model sees, not just what you say to it. Get the full book free when you join the newsletter.
// no spam — one useful email at a time. unsubscribe anytime.
The 6-minute version
A quick tour of the core idea: the context window is working memory, and almost every agent failure traces back to what was inside it.
The grammar of the book
Every technique in agent design — scratchpads, retrieval, summarization, sub-agents — is one of these four moves. The book teaches you when to reach for each one.
Put important information outside the fragile context window, so the agent can survive forgetting.
→ rules files · memory · playbooksLoad only what the next decision requires. Agents get smarter when they see less — the right less.
→ retrieval · tool masking · MCPKeep the meaning, cut the tokens. More useful signal per token on every single model call.
→ summaries · compaction · stateSeparate jobs deserve separate context windows. Keep noisy research out of clean planning.
→ sub-agents · phases · handoffsInside the book
Built for builders
Join the newsletter
The book is on its way. If it doesn’t arrive in a few minutes, check your spam folder — then teach your email client some better context selection.