The Standard Deviation (STDDEV) indicator measures the dispersion of a data series from its mean, often used as a volatility indicator to identify potential trading opportunities and risk management.
AI agents call GetTimeSeriesStdDev to retrieve information from Twelve Data MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a financial data analysis tool that retrieves and calculates technical indicators from market data. While it operates in the financial domain, it performs read-only operations (retrieves/analyzes existing market data) without executing any transactions, modifying records, or committing financial obligations.
From the tool's definition The tool returns calculated volatility metrics (standard deviation) from historical market data. The description indicates it 'measures the dispersion of a data series from its mean' and is used to 'identify potential trading opportunities and risk…
Documented attack patterns abuse exactly the kind of access GetTimeSeriesStdDev gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Twelve Data MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for GetTimeSeriesStdDev:
{
"version": "1",
"default": "deny",
"tools": {
"GetTimeSeriesStdDev": {}
}
}GetTimeSeriesStdDev is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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The Standard Deviation (STDDEV) indicator measures the dispersion of a data series from its mean, often used as a volatility indicator to identify potential trading opportunities and risk management. It is categorised as a Read tool in the Twelve Data MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Twelve Data MCP Server MCP server in PolicyLayer and add a rule for GetTimeSeriesStdDev: 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 Twelve Data MCP Server. Nothing to install.
GetTimeSeriesStdDev 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 GetTimeSeriesStdDev 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 GetTimeSeriesStdDev. 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.
GetTimeSeriesStdDev is provided by the Twelve Data MCP Server MCP server (twelvedata/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 186 Twelve Data MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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186 Twelve Data MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.