Initiates a Slack RTM session providing a single-use WebSocket URL (valid 30s) for event streaming; does not set initial presence status.
Part of the Slack server.
Free to start. No card required.
AI agents invoke SLACK_START_REAL_TIME_MESSAGING_SESSION to trigger processes or run actions in Slack. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
SLACK_START_REAL_TIME_MESSAGING_SESSION can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. PolicyLayer enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
{
"version": "1",
"default": "deny",
"tools": {
"SLACK_START_REAL_TIME_MESSAGING_SESSION": {
"limits": [
{
"counter": "slack_start_real_time_messaging_session_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}See the full Slack policy for all 143 tools.
These attack patterns abuse exactly the kind of access SLACK_START_REAL_TIME_MESSAGING_SESSION gives an agent. Each links to the full case and the policy that stops it:
Other execute tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Initiates a Slack RTM session providing a single-use WebSocket URL (valid 30s) for event streaming; does not set initial presence status.. It is categorised as a Execute tool in the Slack MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Slack MCP server in PolicyLayer and add a rule for SLACK_START_REAL_TIME_MESSAGING_SESSION: 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. Nothing to install.
SLACK_START_REAL_TIME_MESSAGING_SESSION is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the SLACK_START_REAL_TIME_MESSAGING_SESSION 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_START_REAL_TIME_MESSAGING_SESSION. 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_START_REAL_TIME_MESSAGING_SESSION is provided by the Slack MCP server (@modelcontextprotocol/server-slack). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 143 Slack tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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