The Cloverly flight endpoint calculates the typical fuel burn per passenger on a typical flight of a certain distance. Thus, API requests for greening a flight require a distance. But when dealing with flights, people don't typically talk distance. They talk departure and arrival airports.
So our API accepts three-letter IATA (International Air Transport Association) airport codes. Users of Cloverly for Slack can green their flights in Slack by entering commands beginning with "/green" in Slack messages, and then listing the airport codes. For example, this would green a round-trip flight between San Francisco and Frankfurt, Germany, with a connection each way in Atlanta:
/green my flight from sfo to atl to fra to atl to sfo