At the Citi Open in Washington 2019, Andy Murray played doubles with Jamie Murray. The team did not got a wildcard, nor was it a protected ranking (PR). Link to draw.
According to this answer on sports.stackexchange.com, the ranking 6 week before the tournament is relevant for enter a draw. Andy Murray did not have a ranking 6 weeks before, according to ranking history
In the draw it is mentioned, that the last direct acceptance are "Advance-47/On-Site-54". Why was he allowed to play doubles in Washington without wildcard or PR?
Edit:
I found something in the rule book, page 10 about commitment player:
C. Commitment Player
A 2019 ATP commitment player is any player positioned in the Top 30 in the ATP 2018 Rankings (singles) as of November 5, 2018.
...
E. Commitment Player Entry Exception – Top 30
Commitment players are automatically accepted into the main draw of all ATP Tour 500 events in which they have entered in a proper manner.
Commitment players only are single players. Does this count also for doubles main draw?