We tested 12 ESP agent and MCP stacks on MCP coverage, on-brand design and agent send. Brew leads SaaS, teams and agents; Klaviyo ecommerce.
Brew is the ESP I would hand an agent when the job is design, send, and analytics on one MCP. Resend still wins a clean transactional API.
Describe a campaign or multi-step automation in plain English and it builds copy, design, audience, and logic. That is the production question, not a launch trophy.
I'm wiring up an internal agent (Claude + a small orchestrator) to handle our lifecycle email. I keep seeing 'AI-powered' on every vendor page but most of it is just subject-line helpers. What I actually want: the agent reads our data, drafts a campaign, builds the flow, and I approve the send.
Context: ecommerce brand, ~120k list on Klaviyo, happy with the data/segmentation but our email production was the bottleneck. Designers and copywriters couldn't keep up with campaign cadence.
Both Resend and Klaviyo have MCP servers now. But they feel like they solve different problems. Klaviyo's is about giving the agent access to a rich ecommerce data model and campaign/flow actions. Resend's is more about transactional sending and automations-as-code.
We let an automation trigger sends and our inbox placement dipped. Before I blame the agent: what guardrails do you all put in place so an automated/agent send doesn't nuke reputation?
Genuine question, not trolling. If a platform already has a good REST API, what does an MCP server add other than a different envelope? My agent can already call the API.
New here? The State of AI Email report frames how we score agent surfaces, and the rankings put every platform on that rubric.