http://api.wahrungsrechner.org/v1/full/{source}/{format}?key={YOUR_KEY}

Property	Type	Description
source	`string(3)`	The currency source code (3 letters)
format	`string(3)`	`json`, `xml` or `jsonp`
key	`string(128)`	Your free API key

Api result

http://api.wahrungsrechner.org/v1/full/EUR/json?key={YOUR_KEY}