MCP, Skills, and Friends

MCP servers, skills, hooks, and subagents — the tools that extend an agent harness beyond hardcoded tool schemas.

Structured Output

Why structured output is the linchpin — one field determines whether you have a chatbot or an agent.

The Agent Harness

What Claude Code actually is — an agent harness around the Claude API, with an action loop, tools, permissions, and subagents.

OpenAI's Data Agent