Slack Block

The Slack block provides a comprehensive Slack integration with OAuth authentication. Use it to send formatted messages with Slack's mrkdwn syntax, create canvases, read channel messages, or trigger workflows from Slack events like mentions and messages.

Overview

When to Use

• Send notifications or status updates to a Slack channel as part of a workflow.
• Post formatted messages using Slack's mrkdwn syntax (alerts, summaries, reports).
• Create a Slack canvas with a title and markdown content to share rich documents.
• Read recent messages from a channel to ingest context into downstream blocks.
• Trigger a workflow from Slack events such as mentions or new messages via webhook.
• Authenticate with either the managed Zelaxy Bot (OAuth) or your own custom bot token.

Configuration

Operation

Dropdown selecting what the block does. Required. Options:

Defaults to send. The active operation controls which additional fields are shown.

Authentication Method

Dropdown choosing how to authenticate. Required. Options:

Defaults to oauth.

Slack Account

OAuth credential picker for the Slack workspace. Shown when Authentication Method is oauth. Requests the following scopes: channels:read, channels:history, groups:read, groups:history, chat:write, chat:write.public, users:read, files:write, canvases:write.

Bot Token

Password field for entering a Slack bot token (format: xoxb-...). Shown when Authentication Method is bot_token.

Channel (basic mode) / Channel ID (advanced mode)

Channel selector for picking the target Slack channel (basic mode). In advanced mode, enter the raw Slack channel ID directly (e.g., C1234567890). One of these must be provided for every operation.

Message

Long text input for the message body. Supports Slack mrkdwn formatting. Required for the send operation.

Canvas Title

Short text input for the title of the canvas. Required for the canvas operation.

Canvas Content

Long text input for the canvas body (markdown supported). Required for the canvas operation.

Message Limit

Number of messages to retrieve (integer, default 10, capped at 15). Applies to the read operation only.

Oldest Timestamp

ISO 8601 timestamp setting the lower time bound for the messages fetched. Optional, applies to the read operation only.

Trigger Configuration

When the block runs in trigger mode, this field configures the slack_webhook trigger to start the workflow from incoming Slack events (e.g., channel mentions, new messages).

Inputs & Outputs

Inputs:

• operation (string) — Operation to perform (send, canvas, or read)
• authMethod (string) — Authentication method (oauth or bot_token)
• credential (string) — Slack OAuth access token (used with Zelaxy Bot auth)
• botToken (string) — Bot token (used with Custom Bot auth, format xoxb-...)
• channel (string) — Channel identifier from the channel selector
• manualChannel (string) — Manual channel ID override (advanced mode)
• text (string) — Message text for the send operation (supports mrkdwn)
• title (string) — Canvas title for the canvas operation
• content (string) — Canvas content in markdown for the canvas operation
• limit (string) — Maximum number of messages to read for the read operation
• oldest (string) — Oldest timestamp boundary for the read operation

Outputs:

• ts (string) — Message timestamp returned by the Slack API (send operation)
• channel (string) — Channel identifier where the message was sent (send operation)
• canvas_id (string) — Canvas identifier for the created canvas (canvas operation)
• title (string) — Canvas title (canvas operation)
• messages (json) — Array of message objects retrieved from the channel (read operation)
• event_type (string) — Type of Slack event that triggered the workflow (trigger mode)
• channel_name (string) — Human-readable channel name (trigger mode)
• user_name (string) — Username who triggered the event (trigger mode)
• team_id (string) — Slack workspace/team ID (trigger mode)
• event_id (string) — Unique event identifier for the trigger (trigger mode)

Tools

• Slack Message (slack_message) — Sends a message to a Slack channel or user via chat.postMessage. Supports Slack mrkdwn formatting. Returns ts (message timestamp) and channel (channel ID).
• Slack Canvas Writer (slack_canvas) — Creates and shares a collaborative Slack canvas in a channel via canvases.create. Accepts a title and content (markdown). Returns canvas_id, channel, and title.
• Slack Message Reader (slack_message_reader) — Reads the latest messages from a Slack channel via conversations.history with optional limit and oldest time filtering. Returns a messages array where each item has ts, text, user, type, and subtype.

YAML Example

slack_1:
  type: slack
  name: "Slack"
  inputs:
    operation: "send"
    authMethod: "oauth"
    credential: "{{SLACK_OAUTH_TOKEN}}"
    channel: "C1234567890"
    text: "Deployment finished: {{start.input}}"
  connections:
    outgoing:
      - target: next-block-id