The Fantasy Sports APIs provide URIs used to access fantasy sports data. Currently the APIs support retrieval of Fantasy Football, Baseball, Basketball, and Hockey data including game, league, team, and player information. The APIs are based on a RESTful model. Therefore, resources like game, league, team, player etc. and collections like games, leagues, teams, players form the building blocks for these APIs. Each resource is identified by a resource ID, and a collection is identified by its scope, specified in the URI.
Historically, Yahoo! has provided two full draft and trade style fantasy football and baseball games -- a free version, and a plus version (which contains more features and content). With the 2010 seasons, the Free and Plus versions of Football and Baseball have merged. Each game is comprised of many "leagues", which typically contain 8-12 teams, which are managed by one or more users. At the beginning of a league's season, professional athletes ("players") are uniquely assigned or chosen through a draft to each team. The players that are not chosen or assigned are available to be acquired via a free-agent or waiver wire process (a "transaction"). These teams compete against each other based on statistics from real-world competitions based on categories like touchdowns, yards gained, batting average and ERA. Many fantasy sport rules can be set and changed within a league; for instance, the roster positions, statistics used to score, scoring modifiers, and game style are configurable.
The game structure means that a lot of fantasy data is relevant only in the context of a particular league and team. For instance, without the league's scoring rules, the statistics compiled by a player in a real-life competition are not meaningful to a particular league. Three rushing touchdowns by a running back is irrelevant to a league that only considers defensive players. Many leagues are private -- the information about them is only available to users that are a members.