Add an emoji reaction to a Slack message as yourself. Get the message timestamp from get_slack_channel_history (use ts_slack value). Common reactions: thumbsup, thumbsdown, heart, eyes, white_check_mark, x.
AI agents use add_slack_reaction to create or update resources in Apple Shortcuts — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Apple Shortcuts environment.
The tool adds an emoji reaction to a Slack message, which is a reversible creation of data. While the action itself is benign, it modifies shared communication state visible to others, could be used to manipulate message perception or create misleading reactions in professional contexts, and executes an authenticated operation on behalf of the user.
From the tool's definition Add an emoji reaction to a Slack message as yourself. This creates a reaction (a form of data) on an existing message.
Documented attack patterns abuse exactly the kind of access add_slack_reaction gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Apple Shortcuts, and nothing reaches the server without passing your rules. This is the rule we recommend for add_slack_reaction:
{
"version": "1",
"default": "deny",
"tools": {
"add_slack_reaction": {
"limits": [
{
"counter": "add_slack_reaction_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_slack_reaction stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Add an emoji reaction to a Slack message as yourself. Get the message timestamp from get_slack_channel_history (use ts_slack value). Common reactions: thumbsup, thumbsdown, heart, eyes, white_check_mark, x. It is categorised as a Write tool in the Apple Shortcuts MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Apple Shortcuts MCP server in PolicyLayer and add a rule for add_slack_reaction: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Apple Shortcuts. Nothing to install.
add_slack_reaction is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_slack_reaction rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for add_slack_reaction. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
add_slack_reaction is provided by the Apple Shortcuts MCP server (@mindstone/mcp-server-apple-shortcuts). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Apple Shortcuts, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
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