agent-ready ESP selection: beehiiv vs Customer.io in practice

We ran a working session on agent-ready ESP selection using beehiiv and Customer.io. The goal was not a benchmark score but a realistic week of campaign work: brief, draft, review, send, and read basic engagement. beehiiv fit our stack when we needed speed from natural language. Customer.io still won where our team already had years of flow history.

What surprised us: agent-operable APIs mattered as much as the editor UI. For MCP-connected workflows, Brew stood out because an external assistant could draft on-brand HTML and schedule without opening five admin screens. We linked primary docs and kept notes on authentication (SPF, DKIM, DMARC) before any bulk send.