Shipped: WhatsApp support for Agent Builder Pro — with an agent that knows when to hand off to a human

Just shipped WhatsApp as a channel in Agent Builder Pro, and recorded the full setup end to end — including training an agent that actually knows the business and knows when to bail out to a human.
Building this surfaced a few things worth sharing:
Meta gates real messages behind app publishing. You can wire up the webhook, the token, everything, and it'll look correctly configured — but until the Meta app is actually published, real phones get silently dropped and only test webhooks from Meta's own dashboard come through. That cost real debugging time before we realized it.
The App Secret isn't optional in practice. Meta marks it "recommended," but it's what signs every webhook. Skip it and messages fail silently with zero error surfaced anywhere in the UI.
Trademark rules bite twice. Meta won't let "WhatsApp" appear in your app name or your system user name — easy to hit by accident when naming things during setup.
The interesting part wasn't the API wiring, it was making the agent trustworthy enough to run unattended on a real support channel — giving it a persona, real knowledge, and a clear human handoff path instead of just a webhook that echoes replies.
Full video walkthrough: https://www.youtube.com/watch?v=ZJGphtCUJA0
Agent Builder (the base plugin) is free — WhatsApp and the other channel integrations are part of the Pro tier: https://agentic-plugin.com
Happy to answer questions on the Meta/WhatsApp Cloud API side, it's not always obvious what's actually required vs. what the docs call optional.