Each App manages its own Ajv validator instance which you can receive by App#getValidator.
Ajv constructor options may be propvided through options.validator option of App constructor.

Validation & Sanitization as well as Filtering of request / response data can be defined with Route#validate and Route#respondsWith methods respectively.

const route = router.buildRoute({
    type: 'get',
    url : '/',
    summary: 'Get users',
});

route.respondsWith({
    type: 'array',
    additionalProperties: false,
    items: {
        type: 'object',
        additionalProperties: false,
        properties: {
            id       : {type : 'integer'},
            email    : {type : 'string'}
        }
    }
});

route.validate({
    additionalProperties: false, // will remove any other query parameters
    properties: {
        limit: {type: 'integer'},
        offset: {type: 'integer'},
    }
}, 'query'); // possible targets: query | body | params | headers

route.main(function(req, res) {
    return fetchUsersInSomeWay(req.query).then(function(users) {
        // The filter method will make sure the response body has only
        // those data properties which are defined in `respondsWith` schema
        res.filter(users).json();
    });
});