Form Validation: Pattern

Is there any documentation how to create a validation pattern?

For me, I have created a textfield that should only contain a number. so, I tried:

validate:
  required: true
  pattern: [0-9]

But the browser does not recognize this pattern. Did I miss something? Result is a false positive, even if I only insert only numbers, I get a validation error from the browser.

never mind ... found it in the admin docs...