From a baggage perspective, the entire trip would be under the TLS-PHX bag rules of AA, which are "01P" (1 piece) and EACH PIECE UP TO 50 POUNDS/23 KILOGRAMS AND UP TO 62 LINEAR INCHES/158 LINEAR CENTIMETERS

The SEA-PHX segment doesn't count per U.S. policy and it's subsumed by the TLS-PHX rule.

It is a sorry state of affairs when AA itself can't answer the simple question, nor is the baggage allowance displayed along with the price when you buy the ticket.