Check for new messages from your channels and DMs, or get specific messages by ID. TIP: Call this at the start of each session to catch up on context
AI agents call get_messages to retrieve information from Claude Slack without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool purely retrieves message data for informational purposes. It has no side effects—it neither modifies messages, creates channels, executes commands, nor deletes data. The blast radius of misuse is minimal; an agent could potentially read messages it shouldn't have access to, but this is a confidentiality concern rather than a destructive or operational risk.
From the tool's definition Tool description states 'Check for new messages from your channels and DMs, or get specific messages by ID.' The verbs 'check' and 'get' indicate read-only retrieval of existing data with no modification, creation, or deletion capabilities.
Documented attack patterns abuse exactly the kind of access get_messages gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Claude Slack, and nothing reaches the server without passing your rules. This is the rule we recommend for get_messages:
{
"version": "1",
"default": "deny",
"tools": {
"get_messages": {}
}
}get_messages is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Check for new messages from your channels and DMs, or get specific messages by ID. TIP: Call this at the start of each session to catch up on context. It is categorised as a Read tool in the Claude Slack MCP Server, which means it retrieves data without modifying state.
Register the Claude Slack MCP server in PolicyLayer and add a rule for get_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 Claude Slack. Nothing to install.
get_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 get_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 get_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.
get_messages is provided by the Claude Slack MCP server (theo-nash/claude-slack). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Claude Slack, 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.
19 Claude Slack tools catalogued and risk-classified — across an index of 43,000+ MCP servers.