Volume I
First Principles
What an agent is, and is not
An agent is not a prompt with a bag of tools. It is a loop: language in, structured action out, deterministic execution, result appended, repeat. Everything else is a specialization of that loop — or a reason not to use one.
- I.1What an Agent IsAn agent is a loop in which a language model chooses the next structured action, deterministic code executes it, and the result is written back into the context. Personality, frameworks, and 'autonomy' are decorations on that loop.6 min
- I.2Workflows versus AgentsAnthropic draws a bright line: workflows orchestrate LLMs through predefined code paths; agents let the model direct its own process. Most production systems that work are workflows with a small agentic island.7 min
- I.3The Agent LoopContext in, structured next step, execute, append, repeat. Termination is a first-class intent, not an accident of running out of tokens.6 min
- I.4Start SimpleFind the simplest solution, then add complexity only when evaluation says you must. Success is the right system, not the most agentic one.5 min