Amakhosi will go into the two-legged first-round encounter against the Angolan club eyeing a place in the group stage for the first time.
The Glamour Boys reached the first round of the competition after beating Cameroonian champions PWD Bamenda 1-0 on aggregate in the preliminary round.
Shongwe believes Agosto should not be taken lightly at FNB Stadium today (18h00).
"Primeiro Agosto is one of the top teams in Angola and they are not new to the CAF Champions League, they've got quite a number of national team players in the team, so very, very competitive," Shongwe tells snl24.com/kickoff.
"But it doesn't mean they are not beatable. It's a question of using certain advantages that you have. Yes, they are a structured team, they play in this competition on a regular basis. The team that plays at this level you know, it's all about organisation.
"But there's always that outside chance with Chiefs playing at home. You see the thing about this team, in continental football they have higher respect for teams that play in the Champions League, so they might not take it into account that Chiefs are struggling at the moment.
"As a result they will come maybe too defensive sometimes. They know how to play this home and away type of fixtures. So that is where their strength is as well. They have featured regularly in the group stages."
'Cool Cat' says Chiefs should draw inspiration from Eswatini giants Mbabane Swallows, who once eliminated Agosto from the competition in 2018.
"Two years back they lost I think to Mbabane Swallows in the group stages," Shongwe recalls.
"So sure, that is a possibility, yes... and I think Gavin Hunt was there as well in that game. He actually travelled to Swaziland for that game [to prepare for a Bidvest Wits game]."
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