drupal/core/modules/jsonld/jsonld.module

<?php

/**
 * @file
 * Enables entity serialization in JSON-LD.
 */

/**
 * Implements hook_help().
 */
function jsonld_help($path, $args) {
  switch ($path) {
    case 'admin/help#jsonld':
      $output = '';
      $output .= '<p>' . t('The JSON-LD module serializes entities to the <a href="@jsonld_org">JSON-LD</a> data format. To request JSON-LD instead of HTML, a client should add an Accept header to the request. This module will respond with JSON-LD if the Accept header value is one of the following: application/ld+json, which returns an easy-to-use data structure which is compatible with many external schemas, and application/vnd.drupal.ld+json, which is more expressive and is appropriate for content staging.', array(
        '@jsonld_org' => 'http://json-ld.org/',
      )) . '</p>';
      return $output;
  }
}