Your agent's p99 is a different animal
Average latency is the number you demo and the number nobody experiences. A multi-step agent is a sum of random variables, so its total time is dominated by the tail of each step — and the more steps you add, the more certain it becomes that at least one of them is slow. Here’s the model, why the p99 of the whole is worse than the p99 of the parts, and the two levers that actually move it.