Lesson 1: The Agent Function — AgentCraft

An AI agent is just a function that POSTs to an LLM API. Build one from scratch in Python and see what LangChain AgentExecutor, CrewAI, and AutoGen abstract away.

An Agent is a Function Every time you send a message in ChatGPT or Claude, here's what actually happens: your browser sends an HTTP POST to an API, and a response comes back. That's it. The fancy UI, the streaming text, the typing indicator — all cosmetics around one function call. Strip away LangChain's AgentExecutor, CrewAI's Agent, AutoGen's ConversableAgent. At the bottom of every one: a function that sends an HTTP POST and returns the response. That's what you'll build now.

Concepts covered

agent
function
HTTP POST
system prompt
messages

Framework comparison: LangChain's AgentExecutor, CrewAI's Agent, AutoGen's ConversableAgent — wrappers around one function.