Is your feature request related to a problem? Please describe.
As an enterprise, we are running multiple agents in same project, while trying to see the billing its aggregated and doesn't have chargebacks like other GCP services (labels / Tags).

Describe the solution you'd like
From governance point of view, ADK should pass custom labels during execution and GCP finops should honour and incorporate in Billing portal.

Describe alternatives you've considered
One way is to have token count in callback and perform math on pricing.

Additional context
ADK to work closely with FinOps and provide similar capabilities to govern / control LLM cost overshoot and transparency