The API

# app/code/Acme/Locator/etc/schema.graphqls

type Query {
    acmeLocations(
        city: String @doc(description: "Return only locations in this city")
    ): AcmeLocations
    @resolver(class: "Acme\\Locator\\Model\\Resolver\\Locations")
    @doc(description: "Active pickup locations")
    @cache(cacheIdentity: "Acme\\Locator\\Model\\Resolver\\Locations\\Identity")
}

type AcmeLocations @doc(description: "A page of pickup locations") {
    items: [AcmeLocation]!
    total_count: Int!
}

type AcmeLocation @doc(description: "One pickup location") {
    location_id: Int!
    name: String!
    identifier: String!
    city: String
}

<?php
// app/code/Acme/Locator/Model/Resolver/Locations.php
declare(strict_types=1);

namespace Acme\Locator\Model\Resolver;

use Acme\Locator\Api\Data\LocationInterface;
use Acme\Locator\Api\LocationRepositoryInterface;
use Magento\Framework\Api\SearchCriteriaBuilder;
use Magento\Framework\GraphQl\Config\Element\Field;
use Magento\Framework\GraphQl\Query\ResolverInterface;
use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;

class Locations implements ResolverInterface
{
    public function __construct(
        private readonly LocationRepositoryInterface $locationRepository,
        private readonly SearchCriteriaBuilder $searchCriteriaBuilder
    ) {
    }

    public function resolve(
        Field $field,
        $context,
        ResolveInfo $info,
        ?array $value = null,
        ?array $args = null
    ) {
        $this->searchCriteriaBuilder->addFilter(LocationInterface::IS_ACTIVE, 1);

        if (!empty($args['city'])) {
            $this->searchCriteriaBuilder->addFilter(LocationInterface::CITY, $args['city']);
        }

        $results = $this->locationRepository->getList($this->searchCriteriaBuilder->create());
        $items = [];

        foreach ($results->getItems() as $location) {
            $items[] = $location->getData();
        }

        return [
            'items' => $items,
            'total_count' => $results->getTotalCount(),
        ];
    }
}

<?php
// dev/tests/api-functional/testsuite/Acme/Locator/Api/LocationRepositoryTest.php
declare(strict_types=1);

namespace Acme\Locator\Api;

use Magento\Framework\Webapi\Rest\Request;
use Magento\TestFramework\TestCase\WebapiAbstract;

class LocationRepositoryTest extends WebapiAbstract
{
    private const RESOURCE_PATH = '/V1/acme-locator/locations';

    public function testGetListReturnsTheSeededLocations(): void
    {
        $searchCriteria = 'searchCriteria[filterGroups][0][filters][0][field]=is_active'
            . '&searchCriteria[filterGroups][0][filters][0][value]=1'
            . '&searchCriteria[pageSize]=10';

        $serviceInfo = [
            'rest' => [
                'resourcePath' => self::RESOURCE_PATH . '?' . $searchCriteria,
                'httpMethod' => Request::HTTP_METHOD_GET,
            ],
        ];

        $response = $this->_webApiCall($serviceInfo);

        $this->assertArrayHasKey('items', $response);
        $this->assertArrayHasKey('total_count', $response);
        $this->assertGreaterThanOrEqual(2, $response['total_count']);
        $this->assertArrayHasKey('name', $response['items'][0]);
    }
}