AI agents call slack_list_reactions to retrieve information from MCP Slack without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool lists reactions, which is a query/retrieval operation with no side effects or data modification. The server's read-only designation and the pattern of sibling tools confirm this is a Read category tool. Severity is low because retrieving reaction metadata poses minimal risk even if misused by an AI agent.
From the tool's definition Tool name 'slack_list_reactions' indicates retrieval of reaction data. Server is described as 'Secure read-only MCP server for Slack workspaces'. Sibling tools (slack_get_reactions, slack_get_channel_history, slack_get_user_info) are all read operations.
Attacks that exploit this kind of access
slack_list_reactions. It is categorised as a Read tool in the MCP Slack MCP Server, which means it retrieves data without modifying state.
Register the MCP Slack MCP server in PolicyLayer and add a rule for slack_list_reactions: 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 MCP Slack. Nothing to install.
slack_list_reactions is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the slack_list_reactions 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 slack_list_reactions. 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.
slack_list_reactions is provided by the MCP Slack MCP server (pypi:mcp-slack-crunchtools). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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