org-agenda-diary-sexp-prefix

org-agenda-diary-sexp-prefix is a variable defined in `org-agenda.el'.
Its value is

nil

Documentation:
A regexp that matches part of a diary sexp entry
which should be treated as scheduling/deadline information in
`org-agenda'.

For example, you can use this to extract the `diary-remind-message' from
`diary-remind' entries.

You can customize this variable.