The Decoder Kit is the first item that you should get in the Spy Island, though you won’t be needing it if you follow the PoptropicaSecrets cheats and guide for Spy Island.
How to get the Decoder Kit
Arrive at Spy Island by balloon and run to the right and enter the Headquarters building. Jump up to the top until you see a guy wearing a white jacket at bow-tie. This is Director D, the head of your secret agent organization. He’ll give you a Decoder Kit.