Perhaps this will help. According to [Google's Ngram ][1]site, "provocateur" appears in books dating before 1915.

I see this word without "Agent" used in "Testimony of Alexander Orlov" in 1862, page 6: 

> "The name of this provocateur is Mark."




  [1]: https://books.google.com/ngrams/graph?content=%20provocateur&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cprovocateur%3B%2Cc0