Interview D-1 reminder drafts — Juyoung You

A tool that reads the calendar and automatically prepares the reminder email that goes to the candidate the day before an interview — as far as the draft. It does not automate sending. That is the most important decision in this project.

1. At a glance


Role	Design · implementation · operations (solo)
Period	2026-04 – live
Stack	Google Apps Script · Calendar API · Gmail API · clasp
Size	6 source files · 11 commits · integration test suite included
Execution	1 time-based trigger each morning · a separate dry-run mode
Coverage	3 interview types (phone screening · role interview · culture-fit interview)

2. Background — what was the problem

Once an interview is scheduled, a reminder email goes to the candidate the day before. It carries the location, the time, what to bring, and the coordinator’s contact details.

The content itself is standardised. But the template differs by interview type, several can be scheduled on the same day, and above all forgetting one directly damages the candidate’s experience.

So this was the kind of task that is “not hard, but must never be missed”. Having a person check the calendar every day and handle it by hand fails on exactly the days that are busy.

3. What I built

One set of Apps Script that runs automatically each morning.

  Daily morning trigger
        │
        ▼
 ① Fetch tomorrow's events ─ every next-day event in the shared calendar
        │
        ▼
 ② Identify interviews ──── detect the 3 types by title keyword
        │                   (skipped if none match)
        ▼
 ③ Parse candidate details ─ extract name · email from the event description
        │                   ├─ success → on to ④
        │                   └─ failure → into the warning list (not passed over silently)
        ▼
 ④ Duplicate check ─────── skip if a draft with the same subject + recipient exists
        │
        ▼
 ⑤ Create the draft ────── substitute variables into the type's template → Gmail draft
        │                   ※ it does not send
        ▼
 ⑥ Notify the operator ─── send a summary of drafts created + warnings to the running account

4. The most important decision — it does not send

The tool does not send the email automatically; it goes only as far as the draft.

Technically, sending would have been easier. With a draft, a person still has to open their mailbox every day, so on the face of it the automation looks less complete. I chose the draft anyway, for these reasons.

The recipient of this email is a candidate outside the company. Unlike an internal notification, once it goes out wrong it cannot be recalled.
Calendar events depend on fields a person fills in by hand. Events whose time has changed, events that were cancelled, events with an incomplete description exist as a normal matter of course.
In other words, this is a structure where the inputs are not 100% reliable but the output is irreversible. In that combination, the final human check must not be removed.

What I automated is “the writing”; what I did not automate is “the judgement to send”. Almost all of the burden of the repetitive work sat at the front end, so I took most of the benefit without keeping the risk.

5. What I did so that failures are not silent

Parse failures are part of the result

If the candidate’s name or email cannot be found in the event description, that case is not simply skipped. It goes into a warning list with the reason attached, and is carried in the morning summary email.

If it were only skipped, the result would read “3 drafts created”, and nobody would know there had in fact been 4 interviews. Because an omission looks like a success, it has to show up in the output.

I also made the subject of the notification email change with the situation — if there are 0 drafts and only warnings, 확인 필요 (“needs review”) goes into the subject. A morning where nothing happened and a morning where something is wrong have to be distinguishable in the inbox.

It tolerates being run more than once

The trigger can fire twice, and the same schedule sometimes lands in the calendar twice. Before creating a draft, it checks whether a draft with the same subject and recipient already exists, and if so does not create one. That structurally prevents the same reminder being prepared twice for the same candidate.

I kept a separate dry-run

I put the path that only returns what would be created, without creating any drafts, in its own function. When changing a template or adding a keyword, I see the result first without touching the real mailbox.

6. How I made it usable by several coordinators

This script had to keep working as the recruiting owner changed or more of them were added.

① It finds the calendar by name, not by ID Calendar IDs differ per account, so hard-coding an ID means it will not work from another coordinator’s account. Looking it up by name means the same code runs from any account subscribed to that calendar. If it cannot be found, it fails explicitly with the message that the running account must have access to this shared calendar — it does not quietly return 0 results.

② It resolves the notification recipient at run time The summary email goes not to a fixed address but to the account that is running the script. The drafts are created in the running account’s mailbox, so the notification has to reach the same person. Nothing needs reconfiguring when the owner changes.

③ I pulled the interview-type keywords out into configuration Type detection is title-keyword matching, and the keyword list lives in one configuration file. Variant spellings (with or without a space, the English form) sit in the array alongside, so when a new spelling appears I add a line to the list rather than to the code.

7. Results in numbers

Item	Figure
Interview types supported	3 types · a dedicated template per type
What a person did daily	check the calendar → identify the type → pick the template → write → send
What remains after automation	review the draft, then click send
Omission prevention	parse failures promoted to warnings and included in the summary email
Risk of duplicate sending	structurally blocked by the draft duplicate check
Multiple operators	supported by calendar lookup by name and notification based on the running account