IdP Attribute Based on SP Entity ID

[Jason]

I'm running a Shibboleth IdP, and I need to integrate with a couple
different service providers that each want a custom attribute (the
attribute is called "Application").

Each service provider has a different entity ID.  I'm looking for a
way to set a value for the "Application" custom attribute based on the
SP's entity ID.

For example, if the requester's entity ID is
https://service.example.edu/sp, I want the "Application" attribute to
have a value of 2.  If the requester's entity ID is
https://otherservice.example.edu/sp, I'd like the "Application"
attribute to have a value of 3.

What's the best way to accomplish this?  Should I use a scripted attribute?