Most, but not all, of the movies which purport to be about the intelligence community (IC) of this or other countries are clearly fantasies with little basis in reality. But there are some exceptions which show that the filmmakers cared enough to incorporate elements of the reality of this arcane and overly glamourized world into their creative work. This is not to say that the more fantastic and unrealistic of these films, say for example the Bond or Bourne films, are not entertaining, they may be more entertaining in fact. But they are not based at all on the realities.
If we were to have an "Intelligence Film Festival" I would nominate Sicario (2015) by Denis Villeneuve to be on the list. It seems as though the writer and director did know something about this world and used their knowledge to inform the script, at least some of the time. I am not saying the film is totally realistic but it does have some excellent things going for it.
So what criteria might we use to denote a film that is more realistic than the pure entertainment product in this genre?
1. The different agencies of the US Government have different corporate cultures. We do not know much about the Josh Brolin character, but we do know that he is not FBI by his choice of clothes. It is the first thing that the Emily Blunt character notices about him.
2. When Kate is selected, we discover that the Brolin character does not want someone who is from FBI Narcotics, nor who is a lawyer, nor who has worked cases. We are told that Kate is selected for her "tactical skills" but this is revealed later to be not true. See next point where the real reason becomes clear.
3. The Brolin character never actually admits to being CIA, presumably because if you are covert in the CIA (and only a small number of CIA people are), it is not something you readily admit. But we are left near the end believing that he is CIA because he admits that the real reason he wants Kate around is that the CIA (and presumably Delta Force) are not permitted to operate in the continental United States unless there is someone from a domestic agency attached.
4. Ultimately Kate (and the audience) are told that the reason that the team led by Brolin is doing what it is doing is because they have been authorized by much higher authority. By elected representatives in fact, which presumably means either the POTUS or various parties in Congress or both. This is a key point for those of you who have been fed a diet of intelligence movie conspiracy theories. Generally speaking, the intelligence community is not breaking our law (even if they break some other country's law all the time) and they are acting under orders from a legitimate authority. Generally people blame the CIA when they should be blaming their elected representatives, and/or the National Security Council, and/or the POTUS. Generally speaking.
5. At one point Kate pretty much loses her mind and attacks both Alejandro and Matt but we are never really told why. My speculation is because these two are killing a lot of foreign nationals without due process and this would be anathema to a law enforcement official.
6. Why all the mystery about Alejandro? Because Alejandro works for the "competition", e.g. the Columbian drug cartel. Yes the CIA is well-known for dining with sinners.
Now onto some stylistic issues involving the Benicio del Toro character and this film. I wondered just why I found this character so appealing when, after all, without going into any detail here, he does some mighty nasty things. In thinking about this, it occurred to me that he fit a model that was not entirely expected and which may not have been intentional on the part of the filmmakers.
These characteristics include having a mysterious and tragic past, of being very good in a gunfight, of speaking very seldom and then cryptically. He is very secretive about his motivations and his intents. He manages to convince us that while he is cruel, that he may have some worthwhile reasons for his cruelty. Although I am not an expert in such things, he seems very handsome. And of course this all takes place on the border between the US and Mexico and arguably during a time of war.
And while he is successful in some sense of the word, when the film is over he is walking away alone.
Of course the way I have described this, the answer is obvious. He resembles, at least superficially, the Clint Eastwood character in Sergio Leone films. Even if this analogy works for you, and it may not, as I have said before, it is not clear that this was the filmmaker's intent.
Military Rules of Engagement on Wikipedia