I'm trying to use a REST filter to require a certain parameter is set.

Using custom taxonomies and custom posts I've been able to make it so when I request


That the only Cars that come back are ones with a visible_to taxonomy of 123.

However when someone asks for


I want to throw an error, saying that ?visible_to needs to be set.

I've tried hooking into rest_index, rest_pre_dispatch, and some others. Each only fires when I have ?visible_to set in the URL, without them the hooks don't fire.

For example, I would expect this to fire on every REST request

add_filter( 'rest_pre_dispatch','to_limit_access', 1, 3);

function to_limit_access($args, $request, $context) {
  return new WP_Error( 'rest_disabled', __( 'The REST API is disabled on this site.' ), array( 'status' => 404 ) );

But it will only return a WP_Error on






Run without that filter being hit.

Can someone explain why this would be the case and what I can do to avoid it?

I've also tried specific filters like rest_prepare_car but I couldn't get it to fire at all.

2 Answers 2


If you want a parameter to be required for a post type's REST API endpoint you can use the rest_{$this->post_type}_collection_params filter to filter the $args of the GET endpoint:

    function( array $query_params ) {
        $query_params['visible_to']['required'] = true;
        return $query_params;

In turns out we had a caching plugin enabled that was getting in the way of some requests but not others, leading to this inconsistency.

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