svrooij

Since wordpress version 4.9.? wordpress includes the functionality provided by this plugin in the core of wordpress.
Checkout https://developer.wordpress.org/rest-api/using-the-rest-api/global-parameters/#_fields for functionality included in the wordpress core, 
they made it even better by filtering the amount of data pulled from the database.
This plugin will no longer be maintained since it has been superseded by the core functionality.
The <a href="https://wordpress.org/plugins/rest-api/" rel="ugc">wp-rest-api-v2</a> returns a lot of properties. 
It could be very useful (or mobile-data-friendly) to only return the properties needed by the application.
If you only want titles and links of some articles it doesn’t make sense to return the content or the excerpt.
This isn’t limited to posts, it also works on custom posttypes, categories, pages, terms, taxonomies and comments.
Instead of returning:
<pre><code>{
 "id": 2138,
 "date": "2015-10-25T15:31:03",
 "guid": {
 "rendered": "http://worldofict.nl/?p=2138"
 },
 "modified": "2015-10-25T15:31:03",
 "modified_gmt": "2015-10-25T14:31:03",
 "slug": "rechtenvrije-fotos",
 "type": "post",
 "link": "http://worldofict.nl/tip/2138-rechtenvrije-fotos/",
 "title": {
 "rendered": "Rechtenvrije foto’s"
 },
 "content": {
 "rendered": ".. A lot of content .. "
 },
 "excerpt": {
 "rendered": " .. A lot of content ..."
 },
 "author": 2,
 "featured_image": 2139,
 "comment_status": "open",
 "ping_status": "open",
 "sticky": false,
 "format": "standard",
 //.. even more tags ....
}
</code></pre>
It can return (with <code>fields=id,title.rendered,link</code> as GET parameter)
<pre><code>{
 "id": 2138,
 "link": "http://worldofict.nl/tip/2138-rechtenvrije-fotos/",
 "title": {
 "rendered": "Rechtenvrije foto’s"
 }
}
</code></pre>
<h4>Notes</h4>
<ol>
<li>If you specify fields so it wouldn’t return data the default response is send back to the client.</li>
<li>(for developers) something wrong with this plugin? <a href="https://github.com/svrooij/rest-api-filter-fields/" rel="nofollow ugc">Github</a></li>
<li>If you liked the plugin <a href="https://github.com/sponsors/svrooij" rel="nofollow ugc">consider sponsoring me</a></li>
</ol>

REST API – Filter Fields

This is hands-down the best REST API extension available.

Best REST API plugin

Filter the properties returned by the Wordpress rest api V2 (only needed until wordpress 4.9)

Kite

Due to security/privacy concerns, JSON REST API (WP API) only allows post meta data (custom field value) for authenticated users. 
This plugin is an easy way to make post meta available when unauthenticated.
After activate the plugin, go to WP API Customizer option page. 
Click the plus icon to add rows. 
Set JSON attributes and custom field names in your posts that you want to use when unauthenticated. 
The JSON REST API will provide the data as “post_meta” like the following:
<pre><code>"post_meta":{"your_attribute_a":"Custom Field A value","your_attribute_b":"Custom Field B value"}
</code></pre>

WP API Customizer

Make post meta data (custom field values) available for JSON REST API (WP API) when unauthenticated.

REST API – Filter Fields vs WP API Customizer