Slack Command Bot

What it is

A research group's helper, in ~90 lines

A busy team's chat needs a helper — something that lives in Slack and answers questions about the team's activities and software stack. This little bot does exactly that, and it's deliberately tiny, which is exactly why it's a perfect first bot to build from scratch.

Strip away the ambition and what's left is the canonical shape of every chat bot: connect, listen forever, and react when addressed. Learning that skeleton is worth far more than the feature it shipped with.

The stack

Tools under the hood

How it works

The listen loop

The entire bot is one idea repeated forever: read the firehose, check if a message was aimed at me, respond. Here's the skeleton I built to internalise it:

# connect once, then loop forever
if slack.rtm_connect():
    while True:
        events = slack.rtm_read()          # the firehose
        for e in events:
            if AT_BOT in e.get("text", ""):  # was I mentioned?
                cmd = e["text"].split(AT_BOT)[1].strip()
                handle(cmd, e["channel"])     # react
        time.sleep(1)                       # don't busy-spin

1. Find the bot's ID

   A one-off script calls users.list and matches the bot's name to learn its <@ID> mention string.

2. Connect to the firehose

   rtm_connect() opens the WebSocket. From here, every message in the workspace streams in.

3. Filter for mentions

   Most events aren't for the bot. It only acts on messages whose text contains its <@ID>.

4. Parse & respond

   Take the text after the mention, decide what it means, and post a reply back to the same channel.

Reflection

What rebuilding it taught me

• The loop is the whole pattern. Connect, read, filter, react, sleep. Every bot — Discord, Telegram, anything — is a variation on these five lines.
• "Mention" is just string matching. There's no magic routing; the bot literally checks whether its <@ID> appears in the message text.
• Identity is bootstrapped. You need the bot's own ID before it can recognise itself — hence the separate print_bot_id step.
• Secrets belong in the environment. Tokens via env vars, never hardcoded — the first habit of shipping a bot safely.
• RTM is the old way. Rebuilding it also taught me why Slack moved to the Events API + Socket Mode — a persistent firehose loop doesn't scale like webhooks do. Knowing the legacy made the modern design click.