Slack Writer

Sends a message to Slack using a bot token. Supports plain text or rich Block Kit JSON with automatic fallback text for clients that don’t render blocks. Can post to channels, conversations, or open a direct message thread when a user ID is provided.

Usage

Use this node to post notifications, updates, or rich messages to Slack from your Salt pipelines. Provide a bot token, choose a destination (channel name, channel ID, or user ID), and optionally supply Block Kit JSON for rich formatting or a thread timestamp to reply in a thread.

Inputs

Field	Required	Type	Description	Example
slack_token	True	PASSWORD	Slack Bot OAuth token used to authenticate requests. Must include scopes such as chat:write and, if customizing icons, chat:write.customize.
channel	True	STRING	Destination in Slack. Accepts channel name (e.g., #general), channel ID (e.g., C0123456789), or user ID (e.g., U0123456789). If a user ID is supplied, the node opens a DM and posts there.	#general
icon_emoji	True	STRING	Emoji (e.g., :robot_face:) to use as the bot icon. Requires chat:write.customize permission. Leave empty to use the app’s default icon.	:robot_face:
icon_url	True	STRING	URL of a custom bot icon (512x512 or smaller). Requires chat:write.customize permission. Ignored if icon_emoji is set.	https://example.com/icon.png
thread_timestamp	True	STRING	Slack message timestamp to reply in a thread (e.g., 1734479286.246919). Leave empty to start a new top-level message.	1734479286.246919
message	True	STRING	Plain text content of the message. If Block Kit JSON is provided, this is used as a fallback text (auto-generated if omitted).	Hello from Salt AI!
block_kit_json	True	STRING	A JSON array of Slack Block Kit objects for rich formatting. Must be valid JSON and an array of block objects.	[{"type":"section","text":{"type":"mrkdwn","text":"Hello from Salt AI!"}}]

Outputs

Field	Type	Description	Example
status	STRING	The text content of the posted Slack message (final message text).	Hello from Salt AI!
response	STRING	Raw Slack API response serialized as a JSON string.	{"ok": true, "channel": "C0123456789", "ts": "1734479286.246919", "message": {"text": "Hello from Salt AI!"}}
thread_timestamp	STRING	The Slack message timestamp (ts) of the posted message, useful for threading subsequent replies.	1734479286.246919

Important Notes

• Authentication: A valid Slack Bot OAuth token is required.
• Scopes: chat:write is required; chat:write.customize is needed to use icon_emoji or icon_url.
• Destinations: Provide #channel, C-channelID, or U-userID. When using a user ID, the node will open a DM with that user and post there.
• Block Kit: block_kit_json must be a JSON array of blocks. If provided, a fallback text is auto-generated from the blocks for clients that can’t render blocks.
• Threading: Provide thread_timestamp to reply within an existing thread. Omit it to post a top-level message.
• Error Redaction: Any error messages will redact the provided token for safety.
• Hidden Timeout: A hidden timeout parameter controls the Slack SDK request timeout (default 60s).

Troubleshooting

• Invalid token or missing scopes: Ensure the token is correct and the app has chat:write (and chat:write.customize if customizing icons). Reinstall the app if scopes changed.
• Cannot post to channel: Verify the bot is a member of the channel and that the channel/ID is correct. For private channels, invite the bot.
• DM not delivered: If using a user ID, ensure the bot can open a DM with that user and that the user has not disabled DMs from the app.
• Invalid Block Kit JSON: Ensure block_kit_json is valid JSON and a top-level array of block objects. Validate using Slack’s Block Kit Builder.
• Thread timestamp rejected: Confirm the thread_timestamp corresponds to a valid message in the target channel and is properly formatted.
• Rate limits or timeouts: Reduce message frequency, increase the hidden timeout, or implement retries with backoff outside this node.