AI agents use untag_samples to create or update resources in FiftyOne MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your FiftyOne MCP Server environment.
This tool modifies existing data by removing tags from samples. It's a reversible write operation (tags can be re-added), not a destructive deletion of the samples themselves. Misuse could result in loss of tagging/labeling work across many samples, hence medium severity.
From the tool's definition "Remove tags from samples in a dataset"
Documented attack patterns abuse exactly the kind of access untag_samples gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and FiftyOne MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for untag_samples:
{
"version": "1",
"default": "deny",
"tools": {
"untag_samples": {
"limits": [
{
"counter": "untag_samples_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}untag_samples 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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Remove tags from samples in a dataset. It is categorised as a Write tool in the FiftyOne MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the FiftyOne MCP Server MCP server in PolicyLayer and add a rule for untag_samples: 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 FiftyOne MCP Server. Nothing to install.
untag_samples 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 untag_samples 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 untag_samples. 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.
untag_samples is provided by the FiftyOne MCP Server MCP server (voxel51/fiftyone-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from FiftyOne 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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47 FiftyOne MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.