From nfl.com,

For most of his run in Philadelphia, Andy Reid did a nice job identifying and grooming coaching talent. So perhaps we shouldn't be surprised Reid has tabbed a first-time coordinator to run his offense with the Kansas City Chiefs.

Adam Caplan of Sirius XM NFL radio reports that Doug Pederson has joined Reid's staff as offensive coordinator. Alex Marvez of FoxSports also reported the story. Pederson, best known in his playing career as Brett Favre's backup in Green Bay, was Reid's quarterbacks coach in Philadelphia. He helped develop Nick Foles in 2012. Pederson was also Reid's starter in Philadelphia in 1999.
Pederson's hire indicates the Chiefs will run the same West Coast offense that Reid used in Philadelphia. Pederson also played in the system.