AI agents call list_fields to retrieve information from Lark Base MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The 'list_fields' tool retrieves field metadata from a database schema. This is a Read operation—it queries and returns information without creating, modifying, or deleting any data. The low severity reflects minimal blast radius: misuse would only expose schema information, not cause data loss or unauthorized modification.
From the tool's definition Tool name 'list_fields' indicates a listing/querying operation with no modification. The server description explicitly states 'read and write access' with 'inspect schemas' as a read capability.
Documented attack patterns abuse exactly the kind of access list_fields gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Lark Base MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list_fields:
{
"version": "1",
"default": "deny",
"tools": {
"list_fields": {}
}
}list_fields 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.
list_fields. It is categorised as a Read tool in the Lark Base MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Lark Base MCP Server MCP server in PolicyLayer and add a rule for list_fields: 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 Base MCP Server. Nothing to install.
list_fields 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 list_fields 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 list_fields. 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.
list_fields is provided by the Lark Base MCP Server MCP server (lark-base-team/lark-base-mcp-node-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Lark Base MCP Server, 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.
13 Lark Base MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.