Adds support for JMESPath queries to all WP REST API endpoints.
Install as per usual into wp-content/plugins or wp-content/mu-plugins.
The plugin checks REST API requests for the _query parameter; if present it treates this as a JMESPath expression and applies it to the response, e.g.
curl -s --globoff "http://my.wordpress.site/wp-json/wp/v2/pages?_query=[0:2].{id: id, title: title.rendered}"
could be used to select only the first two posts (with the [0:2] slice) and from there build an object with id and title fields selected from id and title.rendered.
The JMESPath site has an interactive tutorial and examples.