If you have four or five agents that need to talk to each other, how would they communicate?

With multiple agents, I would use a central message broker or a service mesh. Each agent publishes messages to a topic (e.g., using Kafka or RabbitMQ) and subscribes to topics it cares about. This pub/sub model decouples agents and allows dynamic scaling. For synchronous interactions, each agent exposes a REST or gRPC endpoint and uses a discovery service (e.g., Consul) to locate peers. I would also define a common schema registry (e.g., Confluent Schema Registry) to enforce message contracts. Idempotency and retry logic are added to handle failures. If the agents are in the same environment, an in‑memory event bus can be used for low‑latency communication. The key decisions revolve around the trade‑off between coupling, latency, and fault tolerance.