Here we see wasteful trailing blanks appended:

GET "http://en.wikipedia.org/w/api.php?action=query&titles=Albert%20Einstein&prop=info&format=yaml"|grep ' $'|cat -e
query: $

pages: $
  - $

If one choses any of the ____fm formats, the only trailing blank is at the end of this line of the raw HTML:
"See ... complete documentation, or "

Version: 1.12.x
Severity: trivial
URL: http://en.wikipedia.org/w/api.php?action=query&titles=Albert%20Einstein&prop=info&format=yaml