Post a rich structured message to Slack with Block Kit support. Can post to channels or reply to threads. Supports plain text, markdown formatting, and rich Block Kit layouts with sections, images, dividers, headers, and more.
AI agents use slack_post_rich_message to create or update resources in Simple Slack — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Simple Slack environment.
This tool creates and sends new messages to Slack, which is a reversible write operation. While posting messages could enable spam or social engineering if misused by an AI agent, the core capability is content creation rather than destruction, execution of arbitrary logic, or financial harm.
From the tool's definition Tool description states 'Post a rich structured message to Slack' — the verb 'post' and explicit capability to send messages to channels or threads indicates creation of new content. No deletion, code execution, or financial transactions are involved.
Attacks that exploit this kind of access
Post a rich structured message to Slack with Block Kit support. Can post to channels or reply to threads. Supports plain text, markdown formatting, and rich Block Kit layouts with sections, images, dividers, headers, and more. It is categorised as a Write tool in the Simple Slack MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Simple Slack MCP server in PolicyLayer and add a rule for slack_post_rich_message: 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 Simple Slack. Nothing to install.
slack_post_rich_message 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 slack_post_rich_message 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_post_rich_message. 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_post_rich_message is provided by the Simple Slack MCP server (bugzy-ai/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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