AI agents call std to retrieve information from FiftyOne MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Standard deviation computation is a read-only analytical operation. It retrieves numeric values from a dataset and performs a mathematical calculation, returning results with no side effects, data modifications, or reversible/irreversible changes. This aligns with the Read category definition of operations that retrieve or query data without side effects.
From the tool's definition Tool name 'std' with description 'Compute the standard deviation of a numeric' indicates a statistical calculation operation that reads numeric data and returns a computed value without modifying or deleting any data.
Documented attack patterns abuse exactly the kind of access std 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 std:
{
"version": "1",
"default": "deny",
"tools": {
"std": {}
}
}std is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Compute the standard deviation of a numeric. It is categorised as a Read tool in the FiftyOne MCP Server MCP Server, which means it retrieves data without modifying state.
Register the FiftyOne MCP Server MCP server in PolicyLayer and add a rule for std: 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.
std 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 std 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 std. 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.
std 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.