let a bot acknowledge a slack message with a reaction

acknowledge the handoff without adding another reply to the channel. a bot can put an existing workspace emoji on the exact slack message you name.

by the dusk bot team · checked 12 november 2026 · how we made this

agree that eyes means received for review, so nobody mistakes it for approval. reactions count as writes and bypass sending approval. tell the bot to ask before reacting if you want each one reviewed.

pixel art: a pink pixel bot and an indigo pixel bot beside the Slack mark on a white tile, a big button and two chat bubbles, on a grassy meadow in front of a calm sea with one small island, one saying "mark the handoff received"

where it helps

stock handoffs: mark a count received when it includes a location and date.
shift reports: acknowledge one after checking its required details.
expense requests: use eyes to mean seen, rather than approved.
delivery updates: add the agreed receipt marker to the exact message.

the short version

the reaction belongs on one exact message. the bot finds it through search or channel history before adding the emoji.

give the workspace emoji's name without colons. it must already exist. if the connected account already added that reaction, slack reports success. the same account cannot stack copies of its reaction.

step by step

connect the workspace. allow read and write for this bot's reaction job.
agree on the meaning. choose an existing emoji and explain what it signals.
try one message. open the message the bot found before it reacts.
watch early runs. inspect automations. pause if incomplete reports get acknowledgements.

send this to your bot

paste this into a chat with your bot

when a message arrives in #stock-handoffs, look for a completed count report with a location and count date. add eyes only to complete reports. it means received for review, not approved. tell me here which report you acknowledged. leave incomplete reports alone. never use a check mark, post a message or claim the figures are correct.

when: when a message arrives in #stock-handoffs
needs: slack read and write for reading messages and adding reactions

what comes back looks like this (an example)

conor: east loft count report, dated today
- eyes added to the report
- quantities still need review

what can go wrong

two similar posts? the bot should ask which one you mean.
custom emoji must already exist. a new name won't create one.
an existing reaction counts as success. the same account will not add a second copy.
slack events arrive at once. your local bot still needs an awake computer and an open dusk app.

permissions and asking first

dusk bot counts Add reaction to message as a change: it alters something in Slack, and the sending setting does not cover it. a bot you allow only to read can never call it.

the permissions Slack asks for to run it: reactions:write.

inputs

input	required	what it is
`name`	yes	Name of the emoji to add as a reaction (e.g., 'thumbsup').
`channel`	yes	ID of the channel where the message to add the reaction to was posted.
`timestamp`	yes	Timestamp of the message to which the reaction will be added.

from composio's catalog for Slack (action SLACK_ADD_REACTION_TO_AN_ITEM, read 12 november 2026⁴). your bot fills these in from what you tell it.

try it in 2 minutes

pick one handoff message
choose an existing emoji and explain its meaning
ask for the reaction on that exact message
open the message in slack and look for the emoji

what it looks like

before

conor posts an east loft count with a date. nobody knows if it reached the reviewer.

after the bot

eyes appears on that report.
meaning: received for review. figures still need review.

an illustration with made-up names and numbers.

mistakes people make

using a check mark for "received"

choose an emoji your team won't mistake for approval.

assuming success means a new reaction

look at who already added that emoji.

questions

does adding a reaction use the message sending approval?

no. it counts as a write. tell the bot to ask before each reaction if you want that checkpoint.

can i use our custom handoff emoji?

yes, if the workspace has it. give the exact name without the outer colons.

will it keep stacking the same emoji on a message?

no. the same account cannot stack copies. slack treats an existing reaction as success.

sources

dusk bot docs: files and apps
dusk bot docs: routines
dusk bot docs: a bot's computer
composio, Slack toolkit (catalog version 20261101_00), checked 12 november 2026

drafted with ai help from the dusk bot docs and the sources listed on this page, then checked against them. if something here is wrong or out of date, write to [email protected].