...
Expression Enabled Fields in API Policies
All expression enabled fields take expressions from the SnapLogic Expression Language and the API Policy Manager functions.
Prerequisite
The Policies Snap Pack in your Org must be set to 436patches25626 for the Key Input Format field to display the URL option and its dependent fields.
Settings
After the March release, this policy is updated to automatically detect the signing algorithm using the JWT token's header and key. Previously, you had to select the HSA algorithm manually via the Signing Algorithm* field. This policy only support RSA, HSA, and ECDSA signed keys.
...