Agent SDK
sdk/agent is the agent loop as a Go library. It receives a fully resolved spec
— a model, a pattern, a system prompt, tools and skills — runs the loop, and
returns the conversation it produced.
It decides nothing. It does not choose a model, authorise a tool, or persist a message; every one of those is handed in per run. So it drops into any Go program, and it is a separate module precisely so that it cannot grow opinions about the platform it was written for.
- Install and first agent: A whole working agent in about forty lines.
- Patterns: ReAct, plan-then-act, ReWOO and reflection — what each costs and when it wins.
- Writing a pattern: The extension point that matters: your rules, in your code, keeping the shipped name.
- MCP servers as tools: Connect a server, get []agent.Tool. The loop never learns MCP exists.
- Tools and skills: Why sixty skills cost one entry in the tool list.
- Steering a run: Saying something to an agent that has already started, and where those words land.
- Structured output: A schema the answer has to fit, and a cheaper model to fit it.
- Sessions: Steering a run no process is holding, and resuming one whose process has gone.
- Examples: Eleven runnable agents, each one a single file. They need no key.
Why it is separate¶
Which tools and skills a run may see is an authorisation decision. Keeping the loop in its own module means that decision cannot leak into it — the compiler refuses the import rather than a reviewer noticing.
The same property is what makes it useful to you: nothing else in the repository comes with it. One direct dependency, no database, no server, no configuration file.
Info
Reference documentation is generated from the source on pkg.go.dev. These pages are the narrative half.