> ## Documentation Index > Fetch the complete documentation index at: https://doc.lucidworks.com/llms.txt > Use this file to discover all available pages before exploring further. # Messaging Services Template Expression Variables [localhost link]: http://localhost:3000/docs/4/fusion-server/reference/template-expressions/messaging-service-variables [mintlify link]: https://doc.lucidworks.com/docs/4/fusion-server/reference/template-expressions/messaging-service-variables [old doc.lw link]: https://doc.lucidworks.com/fusion-server/4.2/397 Messages have a set of variables which correspond to the parts of a system message: import { LwTemplate } from '/snippets/LwTemplate.jsx'; * id * to * from * subject * body * type * schedule A system message is the result of evaluating the following expression: ```xml wrap theme={"dark"} ```