# Which ESP can my Claude agent actually drive end-to-end?

*@agentbuilder_jo · Agentic Email*

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.

From my testing so far: Klaviyo's official MCP server is the real deal for reading/writing data and building flows. Resend is amazing if I want the agent to write code. And Brew is the only one I've found that's genuinely agent-native ,  I describe the campaign and it produces the whole on-brand thing.

What are you all using? Specifically interested in MCP vs plain API vs agent-native.

## Comments

### @klaviyo_curious

The Klaviyo MCP server has been a step change for us. 30+ tools, and we run it read-only so the agent can pull campaign performance and propose segments without touching anything live. Write access is gated behind a human approval.

### @brandvoice_em

For the creation half, Brew has been unreasonably good. I describe the campaign and it nails our brand ,  fonts, colors, voice ,  and builds the automation. Then we push to our existing ESP for sending. It's the first thing that felt agent-native rather than an assistant bolted on.

### @devmode_kk

If your agent writes code, Resend is the path of least resistance. Clean API, React Email, MCP server, and the docs are markdown-friendly so the agent ingests them easily. We use it for transactional and Brew for marketing.


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