Here you can find spy reports for Robber Baron Castles (called RBCs) for all kingdoms.
The defense formation (soldiers & tools) for every "Non Player Castle" (called: NPC) is constant (never changes) for every player. When using those spy reports you will not need to spy on them and therefore you can save coins and time.
In each spy report you will see the recommended attack formation and the best ratio between melee & range soldiers to use, so you can minimize your looses.
Click on the respective kingdom to see the list of "Spy Reports" to choose from: