When wiring RAG, tool calling, and memory together into one agent, what's the most common cause of a slow or expensive request?

Each of those adds its own model call or vector search — retrieval is a search call, tool calling can trigger multiple back-and-forth model round-trips, and memory means resending growing conversation history every time — so an agent doing all three per request can easily rack up 3-5x the latency/cost of a single plain chat call if none of it is cached or bounded.