Building My First Custom Appointment App (Calendly + Brevo + Bolt)

Alright — here's one of those projects that started simple and turned into a full-on rabbit hole.

I needed a way for one member of my team to book appointments on behalf of someone else, using Calendly. Sounds easy, right? But I wanted it to go a bit further — automatically detect the client's timezone, adjust the available time slots, and send out a clean, branded confirmation email that didn't look like it was spat out of a robot.

So here's what I did.

Step 1: The Email Template

I first wrote the email using ChatGPT (of course). It had to look professional but still sound human — something that fits our style at Sentra Capital. Once I was happy with that, I moved on to the fun part.

Step 2: Building the App in Bolt

I built the whole interface in Bolt, which let me connect to the Calendly and Brevo APIs. The person doing the booking just:

Selects the client's timezone (for example, "Kuala Lumpur" or "London").
Chooses how many days ahead to look.
Loads the available slots directly from Calendly.
Fills in the client's name, email, and phone number.
Previews the email.
Sends it via Brevo (cc'ing the advisor taking the meeting).

It's smooth, quick, and removes a ton of room for human error.

Step 3: API Headaches (a.k.a. The Struggle)

The hardest part was getting Calendly and Brevo to talk properly. The APIs love to throw errors when you least expect it — and Brevo especially likes to suspend new accounts just for fun.

At one point, I thought I'd broken everything, but eventually it started behaving again. It's running fine now (touch wood).

Step 4: The Result

Here's what it looks like so far:

Custom Appointment Booking App

It's clean, dark-themed, and ADHD-friendly — no clutter, just the essentials. The person booking can do everything in one place without bouncing between tabs or time zone converters.

Final Thoughts

It's been a lot of "trial and error", but that's the fun of building tools like this. You start with an idea, fight through a few API meltdowns, and end up with something that actually saves everyone time.

Next up, I'll probably integrate live timezone detection and maybe even build a dashboard that tracks all appointments across brokers in real time.