Is this a desirable API for a schema validation library?

validationSchema.js

// default schema factory
import schema from './lib';
// each property type is exported separately with named validation helpers
import string, { max, min, matches, required } from './lib/string';
import number from './lib/number';
import shape from './lib/shape';
import array, { every } from './lib/array';

const validationSchema =
  schema('schemaName',
    shape(
      string('username', [
        // a list of validation fns
        min(1, 'optional error message'),
        max(255, 'too long!'),
        matches(/^[a-zA-Z0-9]+$/, 'is this even a valid regex? who knows!')
      ]),
      array('friendIds', [
        every(number)
      ]),
      // each type also accepts a generic function as a second argument
      array('groups', (groups) => {
        return schema('nestedSchema', shape(
          string('groupName', required)
        );
      })
    )
  );