Here's a list of the fields on the Firehose output

Field	Type	Description	Details
type	String	Source type code name	forums* for Online-Discussions and Messaging Boards, and Reviews mainstream* for News outlets blogs* for, well Blogs
forum	String	URL of the section in the site where the thread was created
forum_title	String	Title of the section in the site where the thread was created
discussion_title	String	Title of the thread
language	String	Language in lower case e.g. “english", "spanish" etc	The exception is "chineset" for Taiwanese Mandarin.
gmt_offset	Int	Time difference between the Publication's timezone and GMT The time zone of the site	Webz does its best to automatically detect the time zone of sites. As an example, <gmt_offset>-7</gmt_offset> means the site is in GMT-7:00
topic_url	String	Thread URL
topic_title	String	Main post title
topic_text	String	Main post text	An empty text field is a valid value since a post could be made only from a title, or if the text field is made from emojis or images.
post_num	Int	Numbered order of post in the thread	The main post ID is 1. The first reply ID is 2 and so on.
post_id	String	Post ID	Typically, derived by truncating the post URL string to extract the anchor hashtag http://www...#post-ID
post_url	String	Post URL	Typically, topic_url followed by #post-ID. To avoid duplication, you should always make sure post_url is followed by the above post_id
post_date	String	Date in YYYYMMDD format
post_time	String	Time in HHMM format	We do not adjust the time zones on the Firehose output and display the date and time of each post as it appears on the site.
username	String	Author name
post_title	String	Post title
post	String	Post content	Note, an empty text field is a valid value since a post could be made only from a title, or if the text field is made from emojis or images.
signature	String	Author’s closing message
external_links	String	external_links
country	String	2 letter ISO country code	To get a full country code list, visit our country codes index.
main_image	String	URL of image
rating	Float	Rating	Discussions that include 1 through 5 Ratings
is_lang_certain	Bool	Detected language certainty
seen_before	Bool	False if the post is newly-crawled or true if seen before on a thread	The "seen before" field can help with deduplicating the content. If you exclude the posts with <seen_before>true</seen_before> you will avoid ingesting the same posts on your end.
accuracy_confidence	Bool	Data extraction accuracy
domain_rank	Int	Domain rank
site_categories	String	Category
reviewed_url	String	Contains the URL of the reviewed entity	Exists only in the reviews feed. In most cases the reviewed_url will be the same as the topic_url without the anchor fragment.
entities	String	persons - a list of identified people names found in the post locations - a list of identified locations found in the post organizations - a list of identified companies/organizations found in the post	Currently available for news and blogs posts in English (excluding the comments)