A patch test for your cart
An AI skincare advisor that knows when not to sell you something.
PatchTest sits at the moment before checkout. It scans your skin, reads what you told us, and gives every item in your cart one of four verdicts, each with a source you can click. The AI proposes. The rules decide.
A 30 second intake
Age band, pregnancy, medication, and the signs you have noticed. You tell us. We never read it off your face.
One selfie, two scans
YouCam AI Skin Analysis scores seven concerns and reads your skin type. YouCam AI Fitzpatrick Skin Type Analysis reads your skin tone.
Every item gets a verdict
An AI proposes a routine. A rules engine with cited sources decides what you should actually be allowed to buy.
Try a real one
Each of these replays a scan that really was run through the YouCam APIs, paired with a declared intake. No photo here belongs to a real person, and no minor was ever scanned: the age on the first one is declared, not read off the face.
A 12 year old with a TikTok routine
Declared age under 13. Three strong actives in the cart.
In the cart
Run it
Eight weeks pregnant, breaking out
Wants the retinoid that was working before.
In the cart
Run it
Dark patches and a 30% peel
Fitzpatrick V from the scan. The peel is the risky part.
In the cartRun it
Painful lumps that leave marks
Reported signs that shopping should not try to solve.
In the cart
Run it
On isotretinoin, wants wax strips
Declared current isotretinoin. Wax and an acid in the cart.
In the cart
Run it
Or let an agent do the checking
The same guardrail runs as an MCP server, so anything that speaks the protocol can send it a cart and get back a verdict per item before it recommends, adds or buys anything. No key, no account, nothing to install, and every tool is read-only.
Claude Code, one line
claude mcp add --transport http patchtest https://patchtest.fly.dev/api/mcpClaude Desktop, Cursor, VS Code, or anything else that takes an HTTP MCP server: paste https://patchtest.fly.dev/api/mcp.
check_cartA verdict per item, with the rule and the source behind it.
list_rulesAll 24 cited rules, caveats included.
list_scansThe recorded scans a check can be judged against.
Full setup, a worked call and the protocol notesOr the browser extension, to check a cart on a shop yourself
Why this needs to exist
- 11
- potentially irritating active ingredients in the average top-viewed children’s skincare video on TikTok. Only 26% of daytime routines included sunscreen. Pediatrics, 2025
- 5–13.5%
- of answers to patient-posed medical questions were rated unsafe across four major language models, measured in late 2024. npj Digital Medicine, 2026
- Held
- California AB 2491 would have barred selling retinoids and acids to under-13s. It died in committee in May 2024, so no store has to do this. AB 2491