AI agents use add_attendees to create or update resources in Lark MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Lark MCP Server environment.
Adding attendees to a calendar event is a Write operation because it modifies calendar state reversibly (attendees can be removed later). While the tool could impact multiple people if misused (e.g., adding unwanted attendees to sensitive meetings), it does not delete data, execute arbitrary code, move money, or trigger irreversible actions.
From the tool's definition Tool description states 'Add attendees to a calendar event on Lark', which modifies an existing calendar event by adding participants. This is a reversible modification operation.
Documented attack patterns abuse exactly the kind of access add_attendees gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Lark MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for add_attendees:
{
"version": "1",
"default": "deny",
"tools": {
"add_attendees": {
"limits": [
{
"counter": "add_attendees_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_attendees stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Add attendees to a calendar event on Lark. It is categorised as a Write tool in the Lark MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Lark MCP Server MCP server in PolicyLayer and add a rule for add_attendees: 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 Lark MCP Server. Nothing to install.
add_attendees 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 add_attendees 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 add_attendees. 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.
add_attendees is provided by the Lark MCP Server MCP server (junyuan-qi/lark-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Lark MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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5 Lark MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.