AIP-3201
Projects and Apps
Guidance
Resource Hierarchy
APIs that utilize an App ID as part of a resource name must include a Project identifier in the parent:
apps/*/items
Must instead be:
projects/*/apps/*/items
Project identifiers must follow Cloud guidance. As App IDs are
globally unique, Firebase APIs should allow the unique resource
lookup pattern, allowing a - in place of a Project
ID/Number. For example:
projects/-/apps/1:111222333444:web:abcdef0123456789/things
Referencing App IDs
When referencing an App ID in an SDK or API field, method, or parameter, the
platform-correct initialism of app_id must be used (as opposed to e.g.
app, application_id, or gmp_app_id).
View on GitHub