diff --git a/readme.md b/readme.md
index 5663591..c9adb58 100644
--- a/readme.md
+++ b/readme.md
@@ -4,8 +4,10 @@ This repo contains backing information for Glowers Radio.
 ## Format
 The `songs.json` format **is only intended for use for Glowers Radio**, and is effectively a living standard as a result. **Live data may change drastically without warning**
 
+If you do wish to use this data for your own purposes, i.e: to make a custom player, you should be caching the songs list so your application has something to fallback to if a breaking change to the format is made.
+
 ```yaml
-required: [ version, songs]
+required: [ version, songs ]
 properties:
   version: { type: integer }
   songs:
@@ -15,6 +17,7 @@ properties:
         id:
           type: string
         tags:
+          description: 'A list of tags used for filtering. Entries are arbitrary, see latest songs list.'
           type: array
           items: [ { type: string } ]
         metadata:
@@ -22,13 +25,36 @@ properties:
           properties:
             title: { type: string }
             artist: { type: string }
+            href:
+              description: 'A URL the original source can be found, if known. Link may be dead'
+              type: string
+              format: url
+            _nigid:
+              description: 'The original song id from nigge.rs. Do not use for nigge.rs detection, use the "niggers" tag instead'
+              type: string
+            _nigkey:
+              description: 'Content of _id from the original nigge.rs song entry. Do not use for nigge.rs detection, use the "niggers" tag instead'
+              type: string
         sources:
           type: array
           items:
           - required: [ type, url ]
             properties:
               type: { type: string, format: mimetype }
-              url: { type: string, format: uri }
-              thumbnail_type: { type: number }
-              thumbnail_url: { format: uri }
+              uri:
+                description: 'A URI that points to the source file. See `GWMediaPlayer.fromURIToAbsolute()` for how to convert to a URL'
+                type: string
+              previews:
+                description: >-
+                  This is an array so GWMediaPlayer can better display videos being played as audio only.
+                  The first Item is how the MediaItem *should* be displayed, other Items are alternative versions the player may use.
+                type: array
+                items:
+                - properties:
+                    display_type:
+                      description: 'Used to determine how the media should be displayed. See GWMediaPlayer.EDisplayType'
+                      type: string
+                    uri: { "$ref": "#/properties/songs/items/properties/sources/items/properties/uri" }
+                    type: { type: string, format: mimetype }
+                    size: { type: string }
 ```