# Previews and quality checks

> How assistants show you the real email, and how Stensul's accessibility and brand checks run on drafts built through the MCP.

Source: https://stensul.com/developers/concepts/previews-and-quality-checks/ · Last reviewed 2026-09-28

## Previews

Tools that change an email return a preview of the result, and `stensul-preview-email` renders one on request. It's the real rendered email, images included, not a mock-up. What you see depends on the host:

| Host | Preview |
| --- | --- |
| Claude, ChatGPT, Gemini Enterprise | Renders inside the chat |
| Writer | A static image |
| Copilot | Opens through the edit link |
| Any host without in-chat rendering | A PNG, or a link to the editor |

If a change doesn't show up, close and reopen the email, especially if it's also open in the Stensul editor.

## Quality checks

`stensul-run-quality-check` runs the same checks Stensul runs in its editor and returns plain-language issues:

```json
{
  "errors": [
    {
      "message": "Image has no alternative text",
      "rule": "<rule id>",
      "locationText": "the 2nd image in the 3rd module"
    }
  ]
}
```

*Shape from the tool's definition. Rule ids vary by account.* An empty `errors` list means the email passed every active check.

What the accessibility check covers, per Stensul's release notes: alt text, color contrast, heading structure, link and button text, language, tables, lists, custom code, focus order, animation and image contrast. It checks rendered email HTML against WCAG 2.1 AA guidance. A clean check isn't a WCAG certification: some things need a person's judgment.

## Alt text

Assistants write alt text as they place images, after looking at each image. When a result ends with an accessibility list of images missing alt text, the email isn't finished: the assistant should describe each image and send all of them in one follow-up call. Review what it wrote; a good description depends on what the image is meant to say.