Slack Add Reaction

Adds an emoji reaction (e.g. :thumbsup:) to a Slack message using reactions.add. Useful as a lightweight acknowledgement that doesn't clutter the channel transcript, and as the natural fire signal for Slack Trigger workflows filtering on reaction_added.

Requires a Slack connection with reactions:write scope.

Configuration

Field	Description	Notes
Connection	Slack connection to use	Required
Channel	Channel name or ID containing the message	Required. Supports templates. e.g. #general or C01234567
Message Timestamp	The message's ts value	Required. Supports templates. Usually wired from an upstream slack_send_message (e.g. {{ st-send.ts }})
Emoji	Emoji name without colons	Required. Default: thumbsup. Examples: white_check_mark, tada, eyes

Output

Returns the Slack API response:

Field	Description
ok	Whether the reaction was added

Self-fire behaviour

Unlike app_mention, Slack does deliver reaction_added events back to the bot's app even when the bot itself added the reaction. That makes this node ideal for ending an action workflow when you want it to fan-out into a slack_trigger workflow filtering on reaction_added — e.g. for integrations:test self-loops, or for chaining workflows together using Slack as the message bus.

Example: chaining two workflows

Action workflow:

1. slack_send_message posts a parent message and outputs its ts.
2. slack_add_reaction reacts to that ts with :white_check_mark:.

Trigger workflow:

1. slack_trigger listens for reaction_added.
2. Receives the event, fans out as needed.

Required scopes

Add reactions:write to the bot's OAuth scopes for this node, and reactions:read if the Slack Trigger workflow filters on reaction_added. Slack will show an "update available" banner when scopes change — workspace admins approve it.