AI agents use update_field_acl to create or update resources in Kintone MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Kintone MCP Server environment.
This tool modifies access control lists (ACLs) for fields in a Kintone app. While reversible (ACLs can be changed again), it has high blast radius because misconfiguration could grant unauthorized access to sensitive data, expose confidential fields, or lock legitimate users out of critical fields.
From the tool's definition Tool name is 'update_field_acl' and description states it updates ('更新します') field access permissions ('アクセス権限') in Kintone apps. This modifies security/access control configuration.
Documented attack patterns abuse exactly the kind of access update_field_acl gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Kintone MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for update_field_acl:
{
"version": "1",
"default": "deny",
"tools": {
"update_field_acl": {
"limits": [
{
"counter": "update_field_acl_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}update_field_acl 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.
Free to start. No card required.
kintoneアプリのフィールドのアクセス権限を更新します. It is categorised as a Write tool in the Kintone MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Kintone MCP Server MCP server in PolicyLayer and add a rule for update_field_acl: 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 Kintone MCP Server. Nothing to install.
update_field_acl 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 update_field_acl 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 update_field_acl. 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.
update_field_acl is provided by the Kintone MCP Server MCP server (r3-yamauchi/kintone-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Kintone 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.
70 Kintone MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.