Vol. III · Single-Agent Patterns · III.2
Routing
Classify the input, then send it to a specialist prompt, model, or workflow. Separation of concerns for language.
5 min read
Doctrine
- Route when categories are stable and classification is cheap and accurate.
- Hard questions to large models, easy ones to small models — routing is also a cost control.
- A misroute should be recoverable: include an 'other' specialist, not a silent drop.
Router as a tiny agent
OpenAI handoffs and Google ADK's LLM-routed hierarchy are routing with an identity. The router should have almost no tools. Its only job is to pick the next specialist. That specialist gets a clean context, not the router's indecision.
Anti-patterns
- A router with twenty fuzzy classes and no eval on the classifier.
- Routing in natural language without a structured label.