AI agents use create_field to create or update resources in Lark Base MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Lark Base MCP Server environment.
Creating a field modifies database schema reversibly—it can be undone by deleting the field. This is Write category, not Destructive, since the operation does not irreversibly destroy data. Severity is medium because unintended field creation could disrupt database structure and downstream queries, but the blast radius is limited to schema changes rather than data loss.
From the tool's definition Tool name 'create_field' indicates it creates/adds a new field to a database table. The server description states it provides 'read and write access to Feishu Base databases' and 'manipulate records through natural language.' Sibling tools include…
Documented attack patterns abuse exactly the kind of access create_field 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 create_field:
{
"version": "1",
"default": "deny",
"tools": {
"create_field": {
"limits": [
{
"counter": "create_field_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_field 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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create_field. It is categorised as a Write tool in the Lark Base MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Lark Base MCP Server MCP server in PolicyLayer and add a rule for create_field: 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.
create_field 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 create_field 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 create_field. 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.
create_field 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.
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13 Lark Base MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.