feishu_send_message · Lark Cli MCP: Risk & Policy

WHAT IT DOES

What feishu_send_message does on Lark Cli

AI agents use feishu_send_message to create or update resources in Lark Cli — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Lark Cli environment.

WHY IT NEEDS A POLICY

Why feishu_send_message needs a policy

This tool sends messages on behalf of the user to groups or individuals. While messages can technically be deleted later, the primary action is to create and deliver content. This is a Write operation because it creates new data (messages) with side effects (recipient notification, message history).

From the tool's definition Tool name 'feishu_send_message' and description '以用户身份发送飞书/Lark 消息到群聊或个人（支持纯文本与 Markdown）' (send Feishu/Lark messages to group chats or individuals as the user's own identity) indicates the tool creates new messages irreversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

feishu_send_message Rate-limited

feishu_send_message 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "feishu_send_message": {
      "limits": [
        {
          "counter": "feishu_send_message_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Lark Cli, so you can run agents against it safely.

FAQ

Questions about feishu_send_message

What does the feishu_send_message tool do? +

以用户身份发送飞书/Lark 消息到群聊或个人（支持纯文本与 Markdown）. It is categorised as a Write tool in the Lark Cli MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on feishu_send_message? +

Register the Lark Cli MCP server in PolicyLayer and add a rule for feishu_send_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 Lark Cli. Nothing to install.

What risk level is feishu_send_message? +

feishu_send_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit feishu_send_message? +

Yes. Add a rate_limit block to the feishu_send_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.

How do I block feishu_send_message completely? +

Set action: deny in the PolicyLayer policy for feishu_send_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.

What MCP server provides feishu_send_message? +

feishu_send_message is provided by the Lark Cli MCP server (yoreland/lark-cli-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.