The Agent jewel is a device in Metal Shadow Prelude used by the Agency. It is a trademark red jewel the size of a large pea which sits on an Agent's forehead. It suppresses the Agent's memories while seated, though which memories remains unspecified in the Prelude. It cannot be removed or destroyed by force.

Noa Rylie demonstrated the ability to remove them by telekinesis, supposedly as a result of the jewels being created from her own DNA. She can absorb mysterious powers from the jewels by crushing them (which she can do easily), earning the ability to throw freeze balls and more. She removes the jewels of Agent Elf, Agent Ghost, Agent Ziare, Agent Lair, Agent Rail, Agent Ex, and Agent Delta throughout the course of the Prelude, therein returning them their former memories as generals of the original Liberation Front.