AI agents call check_iam_permissions to retrieve information from Storage without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves information about existing IAM permissions without creating, modifying, deleting, or executing any actions. It is a diagnostic/informational query, fitting the 'Read' category. The severity is low because permission checks have minimal blast radius—they cannot alter data, trigger operations, or cause financial impact.
From the tool's definition Tool name 'check_iam_permissions' and description 'Tests IAM permissions for a bucket' indicate a query/verification operation with no side effects.
Attacks that exploit this kind of access
Tests IAM permissions for a bucket. It is categorised as a Read tool in the Storage MCP Server, which means it retrieves data without modifying state.
Register the Storage MCP server in PolicyLayer and add a rule for check_iam_permissions: 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 Storage. Nothing to install.
check_iam_permissions 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 check_iam_permissions 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 check_iam_permissions. 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.
check_iam_permissions is provided by the Storage MCP server (@google-cloud/storage-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.