What is sub-tenant?
A sub-tenant is a full tenant created by a scoped call from a parent: it gets its own API key (returned once), its own skill library, vault and runs, and a billing mode chosen at creation. "self" spends from its own balance, optionally seeded by a grant; "parent" bills the parent’s pool with every charge attributed back.
Why it matters
If you are embedding browser automation in your own product, your customers are your tenants, not ours. Provisioning makes that structural rather than something you simulate with one shared key and your own bookkeeping.