Micro Agents

The smallest thing that acts: one signature, a few tools, a typed reply. Most agents in a production codebase should be this size.

import { agent, ai, f, fn } from '@ax-llm/ax';

const llm = ai({ name: 'openai', apiKey: process.env.OPENAI_APIKEY! });

const lookupOrder = fn('lookupOrder')
  .description('Fetch an order record by id')
  .arg('orderId', f.string('Order id, e.g. ord-1042'))
  .returns(f.json('Order record'))
  .handler(async ({ orderId }) => orderStore.get(orderId))
  .build();

const support = agent('ticket:string -> reply:string', {
  functions: [lookupOrder],
});

const out = await support.forward(llm, {
  ticket: 'Where is my order ord-1042?',
});

That is the whole program. There is no prompt to write, no parser to maintain, no retry loop to hand-roll — the signature generates all three, and the reply comes back as typed data.

Zero Config Is The Full Harness

A micro agent is not a lesser mode. With no configuration, agent() already runs the complete pipeline — distiller, executor with a live runtime session, responder — the same machinery the long-horizon tier uses. You just haven’t needed to touch any of it yet. Two practical consequences:

• Typed outputs are the system boundary. The reply is validated against the signature and retried with feedback on mismatch, so downstream code consumes data, not prose.
• Actions really run. Tools execute in the runtime; results are inspected before the agent answers. A micro agent that looks up an order answers from the record it fetched, not from a guess.

Keeping It Micro

• One signature, one job. If the task description needs the word “then”, consider two agents or a flow.
• Pass tools flat — functions: [lookupOrder, sendReply]. At this size every callable is obviously relevant, and flat inline tools are the most reliable shape for small models (grouped discovery earns its keep later, at catalog scale).
• Small models are the point. Micro agents run well on cheap, fast models — see Performance for measured model guidance.

When To Graduate

Move up a tier when one of these appears:

Runnable code: agent examples and the agent() API.