Search for messages across all accessible channels. Requires user token authentication.
AI agents call 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 retrieves and queries message data from Slack channels without creating, modifying, deleting, or executing any operations. It is purely informational. Severity is medium rather than low because search across all accessible channels could expose sensitive communications (private conversations, confidential discussions, credentials in messages) if an AI agent misuses the query parameters, but the tool itself…
From the tool's definition Tool name is 'search_messages' and description states it 'search[es] for messages across all accessible channels.' The server is explicitly described as 'read-only' and enables AI assistants to 'access' Slack workspace data with no modification or deletion…
Attacks that exploit this kind of access
Search for messages across all accessible channels. Requires user token authentication. 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 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.
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 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 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.
search_messages is provided by the Slack MCP Server MCP server (mynghn/slack-mcp-server). 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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