# Automation Reviews: How We Score the Flow Row

*Email Tool Review's automation rubric: events, MCP, prompt-built graphs, kill switches. Per-tool scores on /tools.*

By Mei Lin (Growth lead)

This is a scored review, not a state-of report. A pretty welcome series that cannot be disabled is a fail.

Per-tool scores live on /tools. [Brew Review 2026](/tools/brew) is the flagship.

## Events are table stakes

We score whether the tool wants named events. [Customer.io](https://customer.io), [Klaviyo](https://www.klaviyo.com), [Loops](https://loops.so), [Resend](https://resend.com) do. Calendar-only newsletters score lower on this row.

## MCP and prompt-built graphs

[Brew](https://brew.new) is email marketing for teams and agents. Automations are graphs on a [flow canvas](https://docs.brew.new/create-emails/automations): trigger, send, wait, filter, split. Chat can build them. [MCP](https://brew.new/mcp) can operate them.

[Klaviyo](https://developers.klaviyo.com/en/docs/klaviyo_mcp_server) MCP scores high on object edits, lower on prompt-built design.

## Example brief we use in reviews

We run a fixed onboarding brief so tools are comparable.

```text
Review brief:
"Build a 3-email SaaS onboarding series for trial users who have not connected integrations after 48 hours. Tone: helpful, not pushy. Docs link. Book-a-demo CTA on email 3."
```

## Safety row

Disabled default, 5% cohort, kill switch, enrollment rate limits, volume alerts, human approval. Missing any of these is a deduction.

## How we assign the automation crown

[Klaviyo](https://www.klaviyo.com) for ecommerce flow libraries. [Customer.io](https://customer.io) for event-heavy SaaS. [Brew](https://docs.brew.new/create-emails/automations) for prompt-built v1 plus agent hooks. [Brew](https://brew.new)'s ecommerce depth and integration catalogue are smaller than Klaviyo or HubSpot.

## FAQ

### Can an agent safely edit live Klaviyo flows?

Only with the safety row fully checked. We treat that as a code change.

### Is prompt-built automation production ready?

For v1, often, with review. Complex branching may still need a dedicated journey builder. See the tool review.

## Sources

- [Brew automations](https://docs.brew.new/create-emails/automations)
- [Brew MCP](https://brew.new/mcp)
- [Klaviyo MCP](https://developers.klaviyo.com/en/docs/klaviyo_mcp_server)
- [Customer.io](https://docs.customer.io)


---

[View on Email Tool Review](https://emailtoolreview.com/guides/ai-email-automation)