Hierarchical Agents — The Supervisor Pattern in ADK Java

Roles: supervisor + workers

Supervisor: reads user intent, decides which worker to invoke, aggregates results. Workers: narrow specialists, don't talk to each other directly.

Wiring in ADK Java

public class SupervisorAgent extends LlmAgent {
  private final Map workers = Map.of(
      "research", researchAgent,
      "code", codeAgent,
      "summarize", summaryAgent
  );
  @Override
  public List getTools() {
    return workers.entrySet().stream()
        .map(e -> AgentAsTool.wrap(e.getKey(), e.getValue()))
        .toList();
  }
}

Why workers as tools

Wrapping workers as tools lets the supervisor's model reason about them the same way it reasons about a search or calculator. No special orchestration logic — the runtime handles dispatch.