How many contacts an audience reaches right now — send the exact audience you would send to POST /v1/messaging/broadcast/audience. It is resolved and validated the same way (same filter rules, same ownership checks, same 33040/33041 errors) and counted the same way a send counts it. Nothing is sent — so an audience matching nobody is count: 0, not the 33039 a send returns.

The count is live: contacts joining or leaving your groups change it. For a very large audience counting stops early and exact is false — read count as "more than".

Rate limit: 5 requests per minute — each estimate counts the whole audience.