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Send Message

Sends a message to a Slack channel or direct message. This action supports rich formatting, attachments, blocks, threading, and various customization options for comprehensive Slack messaging.

Overview

  • Purpose: Send messages to Slack channels or direct messages programmatically.
  • Use Cases: Automated notifications, alerts, workflow updates, bot responses, customer communications, team notifications, integration updates.
  • API Method: POST /messages
  • Slack API: Uses Slack’s chat.postMessage API method.
  • Required Scopes: chat:write, users:read.email, im:write

Destination Options

  • Channel ID: Provide a Slack channel ID (e.g., ‘C1234567890’) to send to a specific channel.
  • User Email: Provide a user’s email address to send a direct message. The action automatically resolves the user and opens a DM channel.
  • Required: You must provide either a channel ID or user email - at least one is required.
  • Channel Format: Channel IDs start with ‘C’ for public channels, ‘G’ for private channels/groups, ‘D’ for DMs.

Required Input Fields

Channel OR User Email: Specify either ‘channel’ (channel ID) or ‘useremailid’ (user email address).

Text: Message text content (optional if using blocks or attachments, but recommended for notifications).

Message Content Options

  • Text: Plain text or Slack mrkdwn formatted message content.
  • Blocks: JSON string containing Block Kit blocks for rich, interactive messages.
  • Attachments: JSON string containing legacy message attachments (deprecated, use blocks instead).
  • Markdown Text: Alternative markdown text field (max 12,000 characters).

Message Formatting

  • Mrkdwn: Set to false to disable Slack markup parsing (default: true).
  • Parse: Change how messages are treated (‘full’ or ‘none’).
  • Link Names: Set to true to find and link user groups and channels.
  • Unfurl Links: Enable/disable automatic unfurling of text-based content.
  • Unfurl Media: Enable/disable automatic unfurling of media content.

Bot Customization

  • Username: Override the bot’s display name for this message.
  • Icon Emoji: Set a custom emoji as the bot’s avatar (e.g., ‘:chart_with_upwards_trend:’).
  • Icon URL: Set a custom image URL as the bot’s avatar.
  • As User: Legacy parameter for classic apps to post as the authenticated user.

Threading and Replies

  • Thread TS: Timestamp of the parent message to reply to (creates a threaded reply).
  • Reply Broadcast: Set to true to make the threaded reply visible to everyone in the channel.
  • Threading: Use thread_ts to keep conversations organized in threads.

Advanced Options

  • Metadata: JSON string with event_type and event_payload for message metadata.
  • Current Draft Last Updated TS: Timestamp for draft message updates.
  • Blocks: Use Block Kit for interactive elements, buttons, menus, and rich formatting.
  • Attachments: Legacy structured attachments (use blocks for new implementations).

Direct Message Workflow

  1. Step 1: Action looks up the user by email using users.lookupByEmail API.
  2. Step 2: Action opens a DM conversation using conversations.open API.
  3. Step 3: Message is sent to the resolved DM channel.
  4. Automatic: This entire process is handled automatically when you provide a user email.

Output

  • OK: Boolean indicating if the message was sent successfully.
  • Channel: The channel ID where the message was posted.
  • TS (Timestamp): Unique timestamp identifier for the sent message (use for threading or updates).
  • Message: The complete message object that was posted.
  • Warning: Any warnings from Slack API.
  • Error: Error message if the send failed.
  • Raw JSON: Complete raw response from Slack API.

Required Permissions

[!IMPORTANT] chat:write: Required to send messages to channels.

[!IMPORTANT] users:read.email: Required to look up users by email for DMs.

[!IMPORTANT] im:write: Required to send direct messages to users.

  • User Consent: Users must grant these permissions during OAuth flow.

Error Handling

  • Missing Destination: Throws error if neither channel nor user email is provided.
  • Invalid Channel: Slack returns error if channel ID doesn’t exist or bot lacks access.
  • User Not Found: Throws error if user email doesn’t match any Slack user.
  • DM Failure: Throws error if unable to open DM conversation with user.
  • Retry Logic: Automatically retries failed requests up to 3 times.

Tips

[!TIP] Use channel IDs instead of names for reliability - channel names can change

[!TIP] For DMs, provide user email - the action handles user lookup and channel opening automatically

[!TIP] Save the returned ‘ts’ (timestamp) to reply in threads or update messages later

[!TIP] Use Block Kit (blocks parameter) for rich, interactive messages instead of legacy attachments

[!TIP] Test messages in a test channel before sending to production channels

[!TIP] Set unfurl_links to false for cleaner messages without automatic link previews

[!TIP] Use thread_ts to keep related messages organized in threads

[!TIP] Customize bot appearance with username and icon_emoji for better user experience

[!WARNING] Keep text under 40,000 characters (Slack’s limit) and markdown_text under 12,000

[!WARNING] Use reply_broadcast sparingly - it notifies all channel members

[!TIP] For formatted messages, use Slack’s mrkdwn syntax (bold, italic, code)

[!TIP] Include fallback text even when using blocks for notification compatibility

[!TIP] Store message timestamps for message updates or deletion workflows

[!TIP] Use metadata field to attach custom data for tracking and analytics

[!IMPORTANT] Ensure your OAuth flow requests all three required scopes (chat:write, users:read.email, im:write)

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