Connector - Slack

The Slack connector exposes a Slack workspace as queryable tables and lets flows post messages back to channels. It is a source connector: it has no SQL engine of its own, so its tables are staged automatically into the active engine (e.g. DuckDB) when a query references them.

Configuration

Create a Slack app with a bot token that has the channels:read, channels:history, users:read, and chat:write scopes, then add a connector to your profile:

~/.wvlet/profiles.json

{
  "profiles": [
    {
      "name": "dev",
      "connectors": [
        { "name": "duckdb", "type": "duckdb", "default": true, "catalog": "memory", "schema": "main" },
        { "name": "slack", "type": "slack", "properties": { "token": "${SLACK_TOKEN}" } }
      ]
    }
  ]
}

Optional properties:

• message_fetch_limit: messages fetched per channel when scanning the messages table (default 1000)

Tables

Table	Columns
channels	id, name, is_private, num_members, topic
users	id, name, real_name, is_bot
messages	channel, user, text, ts, thread_ts

-- Channels with the most members
from slack.channels
| order by num_members desc
| limit 10

-- Message counts per channel
from slack.messages
| group by channel
| agg count(*) as messages

Scanning messages reads the recent history of every channel the bot can access, so prefer filtering early and consider a lower message_fetch_limit for large workspaces.

Posting messages from flows

Every profile connector with tools is an activation target under its instance name. The post_message tool posts a stage's output (or an explicit text:) to a channel:

flow daily_report = {
  stage summary = from slack.messages | group by channel | agg count(*) as messages
  stage notify = from summary
    | activate('slack', tool: 'post_message', channel: '#reports')
}

When text: is omitted, the first rows of the stage output are attached as JSON lines.

Posting messages ad hoc

Outside of a flow, the call statement invokes a tool directly:

call slack.post_message(channel: '#reports', text: 'hello from wvlet')

See Working with Multiple Connectors for details on call.