What actually makes a good advertising agency in Trivandrum?

I've been trying to understand how businesses actually choose an advertising agency in Trivandrum.

There are plenty of agencies offering some combination of branding, social media, digital marketing, advertising and creative services. But the actual difference between them isn't always obvious from their websites.

Personally, I think a good agency needs to get three things right:

1. Understand the business problem.
2. Come up with an idea that actually solves it.
3. Know how to take that idea from concept to execution.

I recently came across Antcep Concepts and found their positioning interesting because they seem to sit somewhere between creative agency, advertising and digital marketing.

I'm curious what others look for when choosing an agency in Trivandrum.

Is it portfolio? Strategy? Creative quality? Performance? Industry experience? Or simply whether you feel the team understands your business?