If the purpose is to prevent tendon injuries, then stretching is not really an effective solution.
This article took a look at nearly 2000 articles in Embase and PubMed, and distilled down to 10 representative studies, none of which found that stretching was an effective method for preventing injuries. (On a side note, I have done previous searches on trying to find proof that stretching prevents muscle injury as well, and come up dry).
They did note a couple of items that did show improvement, namely shoe insoles and hormone therapy related to better outcomes for Achilles susceptibility, and they also noted that prophylactic stretching and training could actually increase the risk.
So if you are looking to prevent tendon injuries in an asymptomatic person, stretching is probably not the path you want to pursue.