AI agents call list_folders to retrieve information from Gcp Storage without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and enumerates folder metadata from a GCP Storage bucket without creating, modifying, or destroying any data. It is a read-only query operation with minimal blast radius—an AI agent misusing it could only enumerate bucket contents, not access, modify, or delete actual data.
From the tool's definition Tool name 'list_folders' and description 'List all folders in a bucket' indicate a retrieval operation with no modification or deletion of data.
Documented attack patterns abuse exactly the kind of access list_folders gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Gcp Storage, and nothing reaches the server without passing your rules. This is the rule we recommend for list_folders:
{
"version": "1",
"default": "deny",
"tools": {
"list_folders": {}
}
}list_folders is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all folders in a bucket. It is categorised as a Read tool in the Gcp Storage MCP Server, which means it retrieves data without modifying state.
Register the Gcp Storage MCP server in PolicyLayer and add a rule for list_folders: 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 Gcp Storage. Nothing to install.
list_folders 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_folders 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_folders. 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_folders is provided by the Gcp Storage MCP server (uysalserkan/gcp-storage-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Gcp Storage, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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23 Gcp Storage tools catalogued and risk-classified — across an index of 43,000+ MCP servers.