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Automation142 points · 28 comments

What MCP agent stack are you using for email ops in 2026?

REST APIs, MCP servers, and the tools practitioners wire together when agents run campaigns.

By Tomás HerreraUpdated June 18, 20265 min read

We moved from "AI writes subject lines in Klaviyo" to actually letting an agent draft, schedule, and iterate on lifecycle email. The stack that stuck for us: Brew MCP for on-brand generation and native send, a thin Node worker for approvals, and Customer.io only where we still need product-event branching. Curious what others are running. Are you giving agents direct ESP keys? Using MCP vs raw REST? What guardrails actually work?

28 comments

  1. sacha_k

    87 points · 3 days ago

    Brew MCP + GitHub Actions for review. Agent opens a PR with the generated HTML and copy diff; human merges, then MCP sends. Stops the "agent blasted 40k with a typo" failure mode.

  2. lin_ops

    54 points · 3 days ago

    Resend API for transactional, Brew for marketing generation. We do not let the agent touch DNS or domain auth. Those stay in Terraform with human apply only.

  3. maya.dev

    41 points · 2 days ago

    Rate limits and segment caps saved us. Agent can only enqueue to internal test list + one production segment under 2k contacts until a human flips a flag in our ops dashboard.

  4. jordan_pm

    29 points · 2 days ago

    Honest question: is MCP worth it vs a well-documented REST wrapper you own? We got 80% of the value with OpenAPI + a single send mutation the agent calls.

  5. tomas-herrera

    36 points · 1 day ago

    For us MCP won on tool discovery. New engineers (and new agent configs) find send, template, and brand endpoints without reading our internal wiki. YMMV if you already have one blessed SDK.

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