The Core Pattern
Every coding agent is just this loop:
while True:
response = model(messages, tools)
if response.stop_reason != "tool_use":
return response.text
results = execute(response.tool_calls)
messages.append(results)That's it. The model calls tools until done. Everything else is refinement.
The 5 Versions
Key Concepts
Knowledge Externalization
Traditional AI stores knowledge in parameters (requires training to modify). The new paradigm stores knowledge in documents (edit SKILL.md to change behavior). Cost drops from $10K+ and weeks to free and instant.
Context Caching
LLMs use KV Cache for efficiency. Modifying system prompts or editing history invalidates cache, exploding costs 7-50x. Treat context as append-only log, not editable document.
Tools vs Skills
Tools are capabilities (what the model CAN do: bash, read, write). Skills are knowledge (HOW the model knows to do things: PDF processing, code review checklists).