When are custom thresholds worth it for Images have usable alt text?
When are custom thresholds warranted?
Turn on `visualAltTextReview` when the answer needs judgement rather than pattern matching: when accessibility legislation applies to you, when a campaign is image-heavy enough that alt text carries the message, or when you are certifying a template for long-term reuse. Extend `placeholderAltTexts` when your own tooling stamps a house default — a CMS writing the filename, a design tool writing `Asset 1` — since those pass a presence check while telling a reader nothing.
When should you stay on Standard?
Leave `visualAltTextReview` off for routine high-volume checking, where the source-level result is enough and the extra model call is not worth it on every send. Keep the default placeholder list if your templates are hand-authored and you have no house default value to add. If your images are largely decorative, adding more placeholder values will mostly generate findings on images that are correctly silent.
What do you trade away?
Enabling the visual review adds cost per send, and because it involves judgement its findings are less mechanical than the pattern list's — they are worth more and are argued with more. Extending the placeholder list has the usual risk of over-reach: a short word added to the list will match alt text that legitimately uses it, and `banner` is already borderline for templates where a banner is what the image genuinely is. Supplying your own list replaces the default rather than extending it, so carry the original values forward unless you mean to drop them.
Community Standard vs org Custom
The Standard placeholder list is drawn from values that appear in real templates and describe nothing, which is what keeps it defensible without configuration. Additions are specific to your tooling and belong with whoever owns the templates, retired when the tool that produced them is. Where the check is being run as accessibility evidence, record whether the visual review was enabled — the two settings answer different questions, and a source-only pass should not be presented as a judgement about the rendered experience.
Worked override examples
A public-sector supplier under accessibility obligations sets `visualAltTextReview` to `true` on template certification runs, accepting the extra cost where the output is evidence. A team whose CMS stamps the filename into the alt attribute adds patterns for that convention to `placeholderAltTexts`, catching images that pass a presence check while saying `hero-final-v3`. A retailer running daily promotional sends keeps both defaults for routine checking and enables the visual review only on the seasonal campaigns where images carry the whole offer.
How does an agent call it with parameters?
{
"type": "email",
"validations": [
{
"id": "email-image-alt-text",
"parameters": {
"placeholderAltTexts": [
"image",
"img",
"photo",
"picture",
"graphic",
"icon",
"spacer",
"banner",
"untitled",
"alt text",
"placeholder"
]
}
}
]
}