Building a custom GPT that sets reminder calls

A custom GPT is a version of ChatGPT you shape with your own instructions and tools. If you add the ReminderIt connector to one, it gains a genuinely useful power: it can schedule real outbound phone calls in your account, not just talk about reminders.

This guide walks through connecting ReminderIt to a custom GPT, what the GPT can then do, and how to prove it works with a live test call. Builder menus change over time, so the steps stay deliberately generic about clicks and specific about what matters.

What you are building

A custom GPT with the ReminderIt connector is a focused reminder assistant. You might frame it as a study coach, a caregiver helper or a personal chief-of-staff, and give it standing instructions like always confirm the time zone and keep call wording short.

The connector is the same hosted one every ReminderIt client uses, at https://mcp.reminderit.com, exposing the same set of tools. The custom GPT is just a convenient, reusable wrapper around them.

Add the ReminderIt connector

In the custom GPT builder, open the area where you add actions or connectors and add a custom connector with the URL https://mcp.reminderit.com. You authorise access on a single OAuth screen, so there is no API key to copy into the configuration.

That consent creates a per-client key in your ReminderIt account which you can revoke at any time at reminderit.com/api-keys. Because menu names in the builder shift between updates, look for the connector or actions section rather than a fixed click-path.

What the GPT can then do

Once connected, the GPT can create_reminder for one-off calls with run_at and recurring calls with a cron expression or interval_days. It can review with list_reminders, get_reminder and list_upcoming, and adjust with update_reminder, pause_reminder, resume_reminder, skip_next_occurrence or set_skip_dates.

It can also manage voices with list_voices, preview_voice and set_reminder_voice, check the account with whoami and get_usage, and look after other people with list_recipients and add_recipient, which triggers a consent call to the new person first. Everything happens strictly inside your own account.

Test with test_call

Before you trust the GPT with a real schedule, prove the pipe works. Give it instructions in its system prompt to offer a test, then in conversation say "ring my phone now to check it". The GPT calls test_call and your phone rings immediately with a sample call.

A live test confirms three things at once: the connector is authorised, your phone number is set up, and the voice sounds right. If nothing rings, the fix is almost always re-checking the connection and your account details rather than anything in the GPT's wording.

A worked example

In the builder, set instructions such as: "You schedule ReminderIt calls. Always confirm the user's IANA time zone before creating anything. Keep spoken wording under twelve words." Then, in a test chat, say "Set a weekday 7am wake-up call, Europe/London, saying 'good morning, time to get up'."

The GPT confirms the zone, calls create_reminder with cron 0 7 * * 1-5, and offers list_upcoming to read it back. Ask it to run test_call and you hear the exact voice before the first real morning. From there, sharing or refining the GPT is just editing its instructions.