Search for messages with specific criteria/filters. Use this when: 1) You need to find messages from a specific user, 2) You need messages from a specific date range, 3) You need to search by keywords, 4) You want to filter by channel. This tool is optimized for targeted searches. For general cha...
AI agents call slack_search_messages to retrieve information from Slack MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs query and retrieval operations only. It searches existing messages by user, date, keywords, and channel filters. There are no side effects, data modifications, deletions, or external operations triggered. The low severity reflects minimal risk even if misused—an AI agent searching messages can leak sensitive information but cannot alter Slack data or trigger external actions.
From the tool's definition Tool name 'slack_search_messages' and description states it 'Search[es] for messages with specific criteria/filters' and is used to 'find messages' and 'search by keywords'.
Documented attack patterns abuse exactly the kind of access slack_search_messages gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Slack MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for slack_search_messages:
{
"version": "1",
"default": "deny",
"tools": {
"slack_search_messages": {}
}
}slack_search_messages is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Search for messages with specific criteria/filters. Use this when: 1) You need to find messages from a specific user, 2) You need messages from a specific date range, 3) You need to search by keywords, 4) You want to filter by channel. This tool is optimized for targeted searches. For general channel browsing without filters, use slack_get_channel_history instead. It is categorised as a Read tool in the Slack MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Slack MCP Server MCP server in PolicyLayer and add a rule for slack_search_messages: 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 Slack MCP Server. Nothing to install.
slack_search_messages 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_search_messages 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_search_messages. 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_search_messages is provided by the Slack MCP Server MCP server (ubie-oss/slack-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 11 Slack MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
11 Slack MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.