# Where failover sits relative to the tool loop

A. failover below the advisor (this module)
   tool executions:  1
   trail:            [openai: ok, openai: failed with status 503, claude: ok]
   answer:           Refunded as refund-A17-1 (from claude)
   what claude was sent: UserMessage, AssistantMessage, ToolResponseMessage

B. retry above the advisor (one ChatClient per provider)
   tool executions:  2
   answer:           Refunded as refund-A17-2

C. usage across a two-call tool loop (calls reported 120+15 and 160+12)
   usage on the final ChatResponse: prompt=280 completion=27
   usage summed per model call:     prompt=280 completion=27

D. the same loop with the first call on a cheaper provider (0.75/3.75 then 2.00/10.00)
   priced per model call: 587 microdollars
   total usage at the last provider's price: 830 microdollars