AI agents use move_blob to create or update resources in Gcp Storage — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gcp Storage environment.
Moving a blob is a reversible modification operation—the data persists but its location changes. This is Write rather than Destructive because the blob itself is not deleted, only relocated. While the operation modifies storage state, it can be undone by moving the blob back.
From the tool's definition Tool performs 'move' operation on blob, which modifies the location/metadata of data in Google Cloud Storage. Description indicates it relocates data between bucket locations rather than creating new copies or deleting irreversibly.
Documented attack patterns abuse exactly the kind of access move_blob 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 move_blob:
{
"version": "1",
"default": "deny",
"tools": {
"move_blob": {
"limits": [
{
"counter": "move_blob_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}move_blob 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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Move a blob from one location to another. It is categorised as a Write tool in the Gcp Storage MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Gcp Storage MCP server in PolicyLayer and add a rule for move_blob: 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.
move_blob 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 move_blob 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 move_blob. 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.
move_blob 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.