The agent adds and removes emoji reactions with the message tool's react action. Behavior varies by channel.

Control UI reactions on channel-origin prompts mirror the bot's reaction through the same react action.

How it works

{
  "action": "react",
  "messageId": "msg-123",
  "emoji": "thumbsup"
}

Channel behavior

Discord and Slack 
- Empty `emoji` removes all of the bot's reactions on the message.
- `remove: true` removes just the specified emoji.
Nextcloud Talk 
- Adding reactions only: `emoji` is required and must be non-empty.
- Reaction removal is not wired to a delete call yet. `remove: true` is rejected with an explicit error instead of silently no-oping.
- Requires the Talk bot registered with the `reaction` feature (see [Nextcloud Talk channel docs](/channels/nextcloud-talk)).
Telegram 
- Use `emoji-list` to find allowed standard reactions and numeric custom emoji identifiers. On Telegram, `channels.telegram.actions.reactions` gates both `react` and `emoji-list`, and `emoji-list` returns the reactions allowed in the current chat.
- Empty `emoji` removes the bot's reactions.
- `remove: true` also removes reactions but still requires a non-empty `emoji` for tool validation.
WhatsApp 
- Empty `emoji` removes the bot reaction.
- `remove: true` maps to empty emoji internally (still requires `emoji` in the tool call).
- WhatsApp has one bot reaction slot per message. Sending a new reaction replaces it rather than stacking multiple emoji.
Zalo Personal (zalouser) 
- Requires non-empty `emoji` for both add and remove.
- `remove: true` removes that specific emoji reaction.
Feishu/Lark 
- Uses the same `react` action as other channels (add/remove/list via message reaction IDs), not a separate tool.
- Adding requires non-empty `emoji` (mapped to a Feishu `emoji_type`, e.g. `SMILE`, `THUMBSUP`, `HEART`).
- `remove: true` requires non-empty `emoji` and removes the bot's own reaction matching that emoji type.
- Empty `emoji` with `clearAll: true` removes all of the bot's reactions on the message.
Signal 
- `channels.signal.reactionNotifications` controls inbound reaction notifications. `"off"` disables them. `"own"` (default) emits events when users react to bot messages. `"all"` emits events for all reactions. `"allowlist"` emits events only for senders in `channels.signal.reactionAllowlist`.
iMessage 
- Outbound reactions are iMessage tapbacks (`love`, `like`, `dislike`, `laugh`, `emphasize`, and `question`). `emoji` must map to one of these kinds to add a reaction.
- `remove: true` without a recognized tapback kind removes all tapback kinds. With a recognized kind it removes just that one.

Reaction level

Per-channel reactionLevel throttles how often the agent sends its own reactions. Values: off, ack, minimal, or extensive.

Related