Hi.

with_keywords - A comma separated list of keyword ID's. Only include movies that have one of the ID's added as a keyword.

I assume that means it will return any movie that has any of the keywords.

http://api.themoviedb.org/3/search/keyword?api_key=key&query=submarine 5 results

https://api.themoviedb.org/3/discover/movie?api_key=key&with_keywords=339,207656,222859,226474 0 results

https://api.themoviedb.org/3/discover/movie?api_key=key&with_keywords=226474 1 result

https://api.themoviedb.org/3/discover/movie?api_key=key&with_keywords=222859 2 results

https://api.themoviedb.org/3/discover/movie?api_key=key&with_keywords=222859,226474 0 results

If the parameter is interpreted as Keyword and Keyword, that makes it very difficult to obtains the correct ID.